Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
On Fri, Mar 19, 2021 at 7:35 AM Viresh Kumar wrote:
>
> On 19-03-21, 14:29, Jie Deng wrote:
> > I also see example drivers/i2c/busses/i2c-xiic.c. Some people might think
> > this way is more clearer than
> >
> > updating each member in probe. Basically, I think it's just a matter of
> > personal preference which doesn't
>
> Memory used by one instance of struct i2c_adapter (on arm64):
>
> struct i2c_adapter {
...
> };
>
> So, this extra instance that i2c-xiic.c is creating (and that you want to
> create) is going to waste 1KB of memory and it will never be used.
>
> This is bad coding practice IMHO and it is not really about personal
> preference.
Agreed. At the minimum, it should have been written as an explicit
memcpy() in the few drivers that have that pattern instead of a benign
looking struct assignment, but even then there is nothing good about it
really. Notably, the largest member by far is the 'struct device', and
that by itself should be a red flag as a device is never meant to be
allocated statically (this used to be common in pre-DT days, but
even then was considered bad style).
I suppose the i2c_add_adapter()/i2c_add_numbered_adapter()
interface could be redesigned to handle this better, since every
driver needs to set the same few fields. That however requires finding
someone to spend the effort on coming up with a nice design and
converting lots of drivers over.
Arnd
Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
On 2021/3/19 13:53, Viresh Kumar wrote:
On 16-03-21, 18:35, Jie Deng wrote:
+++ b/drivers/i2c/busses/i2c-virtio.c
+static int virtio_i2c_send_reqs(struct virtqueue *vq,
+ struct virtio_i2c_req *reqs,
+ struct i2c_msg *msgs, int nr)
+{
+ struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr;
+ int i, outcnt, incnt, err = 0;
+
+ for (i = 0; i < nr; i++) {
+ if (!msgs[i].len)
+ break;
+
+ /*
+* Only 7-bit mode supported for this moment. For the address
format,
+* Please check the Virtio I2C Specification.
+*/
+ reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);
+
+ if (i != nr - 1)
+ reqs[i].out_hdr.flags =
cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT);
+
+ outcnt = incnt = 0;
+ sg_init_one(_hdr, [i].out_hdr,
sizeof(reqs[i].out_hdr));
+ sgs[outcnt++] = _hdr;
+
+ reqs[i].buf = i2c_get_dma_safe_msg_buf([i], 1);
You allocate a buffer here, lets see if they are freeing properly or not (I
remember that I gave same feedback earlier as well, but anyway).
"MAY" allocate a buffer here.
+ if (!reqs[i].buf)
+ break;
+
+ sg_init_one(_buf, reqs[i].buf, msgs[i].len);
+
+ if (msgs[i].flags & I2C_M_RD)
+ sgs[outcnt + incnt++] = _buf;
+ else
+ sgs[outcnt++] = _buf;
+
+ sg_init_one(_hdr, [i].in_hdr, sizeof(reqs[i].in_hdr));
+ sgs[outcnt + incnt++] = _hdr;
+
+ err = virtqueue_add_sgs(vq, sgs, outcnt, incnt, [i],
GFP_KERNEL);
+ if (err < 0) {
+ pr_err("failed to add msg[%d] to virtqueue.\n", i);
+ i2c_put_dma_safe_msg_buf(reqs[i].buf, [i], false);
On failure here, you freed the buffers for request "i" but not others..
Others still need to be sent and then be freed.
+ break;
+ }
+ }
+
+ return i;
+}
+
+static int virtio_i2c_complete_reqs(struct virtqueue *vq,
+ struct virtio_i2c_req *reqs,
+ struct i2c_msg *msgs, int nr)
+{
+ struct virtio_i2c_req *req;
+ unsigned int len;
+ int i, j;
+
+ for (i = 0; i < nr; i++) {
+ req = virtqueue_get_buf(vq, );
+ if (!(req && req == [i])) {
+ pr_err("msg[%d]: addr=0x%x is out of order.\n", i,
msgs[i].addr);
+ break;
Since you break here, what will happen to the buffer ? I thought
virtqueue_get_buf() will return a req only once and then you can't access it ?
Will refine it along with the latter loop.
+ }
+
+ if (req->in_hdr.status != VIRTIO_I2C_MSG_OK) {
+ pr_err("msg[%d]: addr=0x%x backend error.\n", i,
msgs[i].addr);
+ break;
+ }
+
+ i2c_put_dma_safe_msg_buf(req->buf, [i], true);
+ }
+
+ /*
+* Detach all the used buffers from the vq and
+* Release unused DMA safe buffer if any.
+*/
+ for (j = i; j < nr; j++) {
+ req = virtqueue_get_buf(vq, );
+ if (req)
+ i2c_put_dma_safe_msg_buf(req->buf, [j], false);
This will come in play only if something failed in the earlier loop ? Or my
understanding incorrect ? Also this should be merged with the above for loop
itself, it is just doing part of it.
Will refine it along with the earlier loop.
+ }
+
+ return i;
+}
+
+static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int
num)
+{
+ struct virtio_i2c *vi = i2c_get_adapdata(adap);
+ struct virtqueue *vq = vi->vq;
+ struct virtio_i2c_req *reqs;
+ unsigned long time_left;
+ int ret, nr;
+
+ reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL);
+ if (!reqs)
+ return -ENOMEM;
+
+ mutex_lock(>lock);
+
+ ret = virtio_i2c_send_reqs(vq, reqs, msgs, num);
+ if (ret == 0)
+ goto err_unlock_free;
+
+ nr = ret;
+ reinit_completion(>completion);
+ virtqueue_kick(vq);
+
+ time_left = wait_for_completion_timeout(>completion, adap->timeout);
+ if (!time_left) {
On error here, we will surely not free the buffers, isn't it ?
Right. Will fix it. Thank you.
+ dev_err(>dev, "virtio i2c backend timeout.\n");
+ ret = -ETIMEDOUT;
+ goto err_unlock_free;
+ }
+
+ ret = virtio_i2c_complete_reqs(vq, reqs, msgs, nr);
+
+err_unlock_free:
+ mutex_unlock(>lock);
+ kfree(reqs);
+ return ret;
+}
Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
On 2021/3/19 14:35, Viresh Kumar wrote:
On 19-03-21, 14:29, Jie Deng wrote:
I also see example drivers/i2c/busses/i2c-xiic.c. Some people might think
this way is more clearer than
updating each member in probe. Basically, I think it's just a matter of
personal preference which doesn't
Memory used by one instance of struct i2c_adapter (on arm64):
struct i2c_adapter {
struct module *owner;/* 0 8 */
unsigned int class;/* 8 4 */
/* XXX 4 bytes hole, try to pack */
const struct i2c_algorithm * algo; /*16 8 */
void * algo_data;/*24 8 */
const struct i2c_lock_operations * lock_ops;/*32 8 */
struct rt_mutexbus_lock; /*4032 */
/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
struct rt_mutexmux_lock; /*7232 */
inttimeout; /* 104 4 */
intretries; /* 108 4 */
struct device dev; /* 112 744 */
/* XXX last struct has 7 bytes of padding */
/* --- cacheline 13 boundary (832 bytes) was 24 bytes ago --- */
long unsigned int locked_flags; /* 856 8 */
intnr; /* 864 4 */
char name[48]; /* 86848 */
/* XXX 4 bytes hole, try to pack */
/* --- cacheline 14 boundary (896 bytes) was 24 bytes ago --- */
struct completion dev_released; /* 92032 */
struct mutex userspace_clients_lock; /* 95232 */
/* --- cacheline 15 boundary (960 bytes) was 24 bytes ago --- */
struct list_head userspace_clients;/* 98416 */
struct i2c_bus_recovery_info * bus_recovery_info; /* 1000 8 */
const struct i2c_adapter_quirks * quirks; /* 1008 8 */
struct irq_domain *host_notify_domain; /* 1016 8 */
/* --- cacheline 16 boundary (1024 bytes) --- */
/* size: 1024, cachelines: 16, members: 19 */
/* sum members: 1016, holes: 2, sum holes: 8 */
/* paddings: 1, sum paddings: 7 */
};
So, this extra instance that i2c-xiic.c is creating (and that you want to
create) is going to waste 1KB of memory and it will never be used.
This is bad coding practice IMHO and it is not really about personal preference.
I will remove that structure and update the members in probe.
Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
On 19-03-21, 14:29, Jie Deng wrote:
> I also see example drivers/i2c/busses/i2c-xiic.c. Some people might think
> this way is more clearer than
>
> updating each member in probe. Basically, I think it's just a matter of
> personal preference which doesn't
Memory used by one instance of struct i2c_adapter (on arm64):
struct i2c_adapter {
struct module *owner;/* 0 8 */
unsigned int class;/* 8 4 */
/* XXX 4 bytes hole, try to pack */
const struct i2c_algorithm * algo; /*16 8 */
void * algo_data;/*24 8 */
const struct i2c_lock_operations * lock_ops;/*32 8 */
struct rt_mutexbus_lock; /*4032 */
/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
struct rt_mutexmux_lock; /*7232 */
inttimeout; /* 104 4 */
intretries; /* 108 4 */
struct device dev; /* 112 744 */
/* XXX last struct has 7 bytes of padding */
/* --- cacheline 13 boundary (832 bytes) was 24 bytes ago --- */
long unsigned int locked_flags; /* 856 8 */
intnr; /* 864 4 */
char name[48]; /* 86848 */
/* XXX 4 bytes hole, try to pack */
/* --- cacheline 14 boundary (896 bytes) was 24 bytes ago --- */
struct completion dev_released; /* 92032 */
struct mutex userspace_clients_lock; /* 95232 */
/* --- cacheline 15 boundary (960 bytes) was 24 bytes ago --- */
struct list_head userspace_clients;/* 98416 */
struct i2c_bus_recovery_info * bus_recovery_info; /* 1000 8 */
const struct i2c_adapter_quirks * quirks; /* 1008 8 */
struct irq_domain *host_notify_domain; /* 1016 8 */
/* --- cacheline 16 boundary (1024 bytes) --- */
/* size: 1024, cachelines: 16, members: 19 */
/* sum members: 1016, holes: 2, sum holes: 8 */
/* paddings: 1, sum paddings: 7 */
};
So, this extra instance that i2c-xiic.c is creating (and that you want to
create) is going to waste 1KB of memory and it will never be used.
This is bad coding practice IMHO and it is not really about personal preference.
--
viresh
Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
On 2021/3/19 13:40, Viresh Kumar wrote: On 19-03-21, 13:31, Jie Deng wrote: On 2021/3/19 11:54, Viresh Kumar wrote: On 18-03-21, 15:52, Arnd Bergmann wrote: Allowing multiple virtio-i2c controllers in one system, and multiple i2c devices attached to each controller is clearly something that has to work. Good. I don't actually see a limitation though. Viresh, what is the problem you see for having multiple controllers? I thought this would be a problem in that case as we are using the global virtio_adapter here. + vi->adap = _adapter; + i2c_set_adapdata(vi->adap, vi); Multiple calls to probe() will end up updating the same pointer inside adap. + vi->adap->dev.parent = >dev; Same here, overwrite. + /* Setup ACPI node for controlled devices which will be probed through ACPI */ + ACPI_COMPANION_SET(>adap->dev, ACPI_COMPANION(pdev)); + vi->adap->timeout = HZ / 10; These may be fine, but still not ideal I believe. + ret = i2c_add_adapter(vi->adap); i This should be a problem as well, we must be adding this to some sort of list, doing some RPM stuff, etc ? Jie, the solution is to allocate memory for adap at runtime in probe and remove the virtio_adapter structure completely. If you want to support that. Then I think we don't need to change the following at all. + .algo = _algorithm, + + return ret; + + vi->adap = virtio_adapter; This is strange, why are you allocating memory for adapter twice ? Once for virtio_adapter and once for vi->adap ? Either fill the fields directly for v->adap here and remove virtio_adapter or make vi->adap a pointer. Yes, your previous version was partly okay but you don't need the virtio_algorithm structure to be allocated. There are only 4 fields you are updating here, just fill them directly in vi->adap. (FWIW, I also suggested the same when I said "Either fill the fields directly for v->adap here and remove virtio_adapter". ) See how drivers/i2c/busses/i2c-versatile.c and most of the other drivers have done it. I also see example drivers/i2c/busses/i2c-xiic.c. Some people might think this way is more clearer than updating each member in probe. Basically, I think it's just a matter of personal preference which doesn't solve any problems.
Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
On 16-03-21, 18:35, Jie Deng wrote:
> +++ b/drivers/i2c/busses/i2c-virtio.c
> +static int virtio_i2c_send_reqs(struct virtqueue *vq,
> + struct virtio_i2c_req *reqs,
> + struct i2c_msg *msgs, int nr)
> +{
> + struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr;
> + int i, outcnt, incnt, err = 0;
> +
> + for (i = 0; i < nr; i++) {
> + if (!msgs[i].len)
> + break;
> +
> + /*
> + * Only 7-bit mode supported for this moment. For the address
> format,
> + * Please check the Virtio I2C Specification.
> + */
> + reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);
> +
> + if (i != nr - 1)
> + reqs[i].out_hdr.flags =
> cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT);
> +
> + outcnt = incnt = 0;
> + sg_init_one(_hdr, [i].out_hdr,
> sizeof(reqs[i].out_hdr));
> + sgs[outcnt++] = _hdr;
> +
> + reqs[i].buf = i2c_get_dma_safe_msg_buf([i], 1);
You allocate a buffer here, lets see if they are freeing properly or not (I
remember that I gave same feedback earlier as well, but anyway).
> + if (!reqs[i].buf)
> + break;
> +
> + sg_init_one(_buf, reqs[i].buf, msgs[i].len);
> +
> + if (msgs[i].flags & I2C_M_RD)
> + sgs[outcnt + incnt++] = _buf;
> + else
> + sgs[outcnt++] = _buf;
> +
> + sg_init_one(_hdr, [i].in_hdr, sizeof(reqs[i].in_hdr));
> + sgs[outcnt + incnt++] = _hdr;
> +
> + err = virtqueue_add_sgs(vq, sgs, outcnt, incnt, [i],
> GFP_KERNEL);
> + if (err < 0) {
> + pr_err("failed to add msg[%d] to virtqueue.\n", i);
> + i2c_put_dma_safe_msg_buf(reqs[i].buf, [i], false);
On failure here, you freed the buffers for request "i" but not others..
> + break;
> + }
> + }
> +
> + return i;
> +}
> +
> +static int virtio_i2c_complete_reqs(struct virtqueue *vq,
> + struct virtio_i2c_req *reqs,
> + struct i2c_msg *msgs, int nr)
> +{
> + struct virtio_i2c_req *req;
> + unsigned int len;
> + int i, j;
> +
> + for (i = 0; i < nr; i++) {
> + req = virtqueue_get_buf(vq, );
> + if (!(req && req == [i])) {
> + pr_err("msg[%d]: addr=0x%x is out of order.\n", i,
> msgs[i].addr);
> + break;
Since you break here, what will happen to the buffer ? I thought
virtqueue_get_buf() will return a req only once and then you can't access it ?
> + }
> +
> + if (req->in_hdr.status != VIRTIO_I2C_MSG_OK) {
> + pr_err("msg[%d]: addr=0x%x backend error.\n", i,
> msgs[i].addr);
> + break;
> + }
> +
> + i2c_put_dma_safe_msg_buf(req->buf, [i], true);
> + }
> +
> + /*
> + * Detach all the used buffers from the vq and
> + * Release unused DMA safe buffer if any.
> + */
> + for (j = i; j < nr; j++) {
> + req = virtqueue_get_buf(vq, );
> + if (req)
> + i2c_put_dma_safe_msg_buf(req->buf, [j], false);
This will come in play only if something failed in the earlier loop ? Or my
understanding incorrect ? Also this should be merged with the above for loop
itself, it is just doing part of it.
> + }
> +
> + return i;
> +}
> +
> +static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> int num)
> +{
> + struct virtio_i2c *vi = i2c_get_adapdata(adap);
> + struct virtqueue *vq = vi->vq;
> + struct virtio_i2c_req *reqs;
> + unsigned long time_left;
> + int ret, nr;
> +
> + reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL);
> + if (!reqs)
> + return -ENOMEM;
> +
> + mutex_lock(>lock);
> +
> + ret = virtio_i2c_send_reqs(vq, reqs, msgs, num);
> + if (ret == 0)
> + goto err_unlock_free;
> +
> + nr = ret;
> + reinit_completion(>completion);
> + virtqueue_kick(vq);
> +
> + time_left = wait_for_completion_timeout(>completion, adap->timeout);
> + if (!time_left) {
On error here, we will surely not free the buffers, isn't it ?
> + dev_err(>dev, "virtio i2c backend timeout.\n");
> + ret = -ETIMEDOUT;
> + goto err_unlock_free;
> + }
> +
> + ret = virtio_i2c_complete_reqs(vq, reqs, msgs, nr);
> +
> +err_unlock_free:
> + mutex_unlock(>lock);
> + kfree(reqs);
> + return ret;
> +}
--
viresh
Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
On 19-03-21, 13:31, Jie Deng wrote: > > On 2021/3/19 11:54, Viresh Kumar wrote: > > On 18-03-21, 15:52, Arnd Bergmann wrote: > > > Allowing multiple virtio-i2c controllers in one system, and multiple i2c > > > devices attached to each controller is clearly something that has to work. > > Good. > > > > > I don't actually see a limitation though. Viresh, what is the problem > > > you see for having multiple controllers? > > I thought this would be a problem in that case as we are using the global > > virtio_adapter here. > > > > + vi->adap = _adapter; > > + i2c_set_adapdata(vi->adap, vi); > > > > Multiple calls to probe() will end up updating the same pointer inside adap. > > > > + vi->adap->dev.parent = >dev; > > > > Same here, overwrite. > > > > + /* Setup ACPI node for controlled devices which will be probed > > through ACPI */ > > + ACPI_COMPANION_SET(>adap->dev, ACPI_COMPANION(pdev)); > > + vi->adap->timeout = HZ / 10; > > > > These may be fine, but still not ideal I believe. > > > > + ret = i2c_add_adapter(vi->adap); > > i > > This should be a problem as well, we must be adding this to some sort of > > list, > > doing some RPM stuff, etc ? > > > > Jie, the solution is to allocate memory for adap at runtime in probe and > > remove > > the virtio_adapter structure completely. > > > If you want to support that. Then I think we don't need to change the > following at all. > > > + .algo = _algorithm, > > + > > + return ret; > > + > > + vi->adap = virtio_adapter; > This is strange, why are you allocating memory for adapter twice ? > Once for virtio_adapter and once for vi->adap ? Either fill the fields > directly for v->adap here and remove virtio_adapter or make vi->adap a > pointer. Yes, your previous version was partly okay but you don't need the virtio_algorithm structure to be allocated. There are only 4 fields you are updating here, just fill them directly in vi->adap. (FWIW, I also suggested the same when I said "Either fill the fields directly for v->adap here and remove virtio_adapter". ) See how drivers/i2c/busses/i2c-versatile.c and most of the other drivers have done it. -- viresh
Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
On 2021/3/19 11:54, Viresh Kumar wrote: On 18-03-21, 15:52, Arnd Bergmann wrote: Allowing multiple virtio-i2c controllers in one system, and multiple i2c devices attached to each controller is clearly something that has to work. Good. I don't actually see a limitation though. Viresh, what is the problem you see for having multiple controllers? I thought this would be a problem in that case as we are using the global virtio_adapter here. + vi->adap = _adapter; + i2c_set_adapdata(vi->adap, vi); Multiple calls to probe() will end up updating the same pointer inside adap. + vi->adap->dev.parent = >dev; Same here, overwrite. + /* Setup ACPI node for controlled devices which will be probed through ACPI */ + ACPI_COMPANION_SET(>adap->dev, ACPI_COMPANION(pdev)); + vi->adap->timeout = HZ / 10; These may be fine, but still not ideal I believe. + ret = i2c_add_adapter(vi->adap); i This should be a problem as well, we must be adding this to some sort of list, doing some RPM stuff, etc ? Jie, the solution is to allocate memory for adap at runtime in probe and remove the virtio_adapter structure completely. If you want to support that. Then I think we don't need to change the following at all. + .algo = _algorithm, + + return ret; + + vi->adap = virtio_adapter; This is strange, why are you allocating memory for adapter twice ? Once for virtio_adapter and once for vi->adap ? Either fill the fields directly for v->adap here and remove virtio_adapter or make vi->adap a pointer.
Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
On 18-03-21, 15:52, Arnd Bergmann wrote: > Allowing multiple virtio-i2c controllers in one system, and multiple i2c > devices attached to each controller is clearly something that has to work. Good. > I don't actually see a limitation though. Viresh, what is the problem > you see for having multiple controllers? I thought this would be a problem in that case as we are using the global virtio_adapter here. + vi->adap = _adapter; + i2c_set_adapdata(vi->adap, vi); Multiple calls to probe() will end up updating the same pointer inside adap. + vi->adap->dev.parent = >dev; Same here, overwrite. + /* Setup ACPI node for controlled devices which will be probed through ACPI */ + ACPI_COMPANION_SET(>adap->dev, ACPI_COMPANION(pdev)); + vi->adap->timeout = HZ / 10; These may be fine, but still not ideal I believe. + ret = i2c_add_adapter(vi->adap); i This should be a problem as well, we must be adding this to some sort of list, doing some RPM stuff, etc ? Jie, the solution is to allocate memory for adap at runtime in probe and remove the virtio_adapter structure completely. -- viresh
Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
On Thu, Mar 18, 2021 at 3:42 PM Enrico Weigelt, metux IT consult wrote: > > On 16.03.21 08:44, Viresh Kumar wrote: > > > FWIW, this limits this driver to support a single device ever. We > > can't bind multiple devices to this driver now. Yeah, perhaps we will > > never be required to do so, but who knows. > > Actually, I believe multiple devices really should be possible. > > The major benefit of virtio-i2c is either bridging certan real bus'es > into a confined workload, or creating virtual hw testbeds w/o having to > write a complete emulation (in this case, for dozens of different i2c > controllers) - and having multiple i2c interfaces in one machine isn't > exactly rare. Allowing multiple virtio-i2c controllers in one system, and multiple i2c devices attached to each controller is clearly something that has to work. I don't actually see a limitation though. Viresh, what is the problem you see for having multiple controllers? Arnd
Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
On 16.03.21 08:44, Viresh Kumar wrote: FWIW, this limits this driver to support a single device ever. We can't bind multiple devices to this driver now. Yeah, perhaps we will never be required to do so, but who knows. Actually, I believe multiple devices really should be possible. The major benefit of virtio-i2c is either bridging certan real bus'es into a confined workload, or creating virtual hw testbeds w/o having to write a complete emulation (in this case, for dozens of different i2c controllers) - and having multiple i2c interfaces in one machine isn't exactly rare. --mtx -- --- Hinweis: unverschlüsselte E-Mails können leicht abgehört und manipuliert werden ! Für eine vertrauliche Kommunikation senden Sie bitte ihren GPG/PGP-Schlüssel zu. --- Enrico Weigelt, metux IT consult Free software and Linux embedded engineering i...@metux.net -- +49-151-27565287
Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
On 16-03-21, 18:35, Jie Deng wrote:
> diff --git a/drivers/i2c/busses/i2c-virtio.c b/drivers/i2c/busses/i2c-virtio.c
> +struct virtio_i2c {
> + struct virtio_device *vdev;
> + struct completion completion;
> + struct i2c_adapter *adap;
> + struct mutex lock;
> + struct virtqueue *vq;
> +};
> +static struct i2c_adapter virtio_adapter = {
> + .owner = THIS_MODULE,
> + .name = "Virtio I2C Adapter",
> + .class = I2C_CLASS_DEPRECATED,
> + .algo = _algorithm,
> +};
And FWIW, I still have my concerns about mutex-lock and
I2C_CLASS_DEPRECATED, but yeah we need Wolfram to confirm on them.
LGTM otherwise.
--
viresh
Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver
On 16-03-21, 18:35, Jie Deng wrote:
> +static struct i2c_adapter virtio_adapter = {
> + .owner = THIS_MODULE,
> + .name = "Virtio I2C Adapter",
> + .class = I2C_CLASS_DEPRECATED,
> + .algo = _algorithm,
> +};
> +
> +static int virtio_i2c_probe(struct virtio_device *vdev)
> +{
> + struct device *pdev = vdev->dev.parent;
> + struct virtio_i2c *vi;
> + int ret;
> +
> + vi = devm_kzalloc(>dev, sizeof(*vi), GFP_KERNEL);
> + if (!vi)
> + return -ENOMEM;
> +
> + vdev->priv = vi;
> + vi->vdev = vdev;
> +
> + mutex_init(>lock);
> + init_completion(>completion);
> +
> + ret = virtio_i2c_setup_vqs(vi);
> + if (ret)
> + return ret;
> +
> + vi->adap = _adapter;
> + i2c_set_adapdata(vi->adap, vi);
> + vi->adap->dev.parent = >dev;
FWIW, this limits this driver to support a single device ever. We
can't bind multiple devices to this driver now. Yeah, perhaps we will
never be required to do so, but who knows.
--
viresh
[PATCH v8] i2c: virtio: add a virtio i2c frontend driver
Add an I2C bus driver for virtio para-virtualization.
The controller can be emulated by the backend driver in
any device model software by following the virtio protocol.
The device specification can be found on
https://lists.oasis-open.org/archives/virtio-comment/202101/msg8.html.
By following the specification, people may implement different
backend drivers to emulate different controllers according to
their needs.
Co-developed-by: Conghui Chen
Signed-off-by: Conghui Chen
Signed-off-by: Jie Deng
---
Changes in v8:
- Make virtio_i2c.adap a pointer.
- Mark members in virtio_i2c_req with cacheline_aligned.
Changes in v7:
- Remove unused headers.
- Update Makefile and Kconfig.
- Add the cleanup after completing reqs.
- Avoid memcpy for data marked with I2C_M_DMA_SAFE.
- Fix something reported by kernel test robot.
Changes in v6:
- Move struct virtio_i2c_req into the driver.
- Use only one buf in struct virtio_i2c_req.
Changes in v5:
- The first version based on the acked specification.
drivers/i2c/busses/Kconfig | 11 ++
drivers/i2c/busses/Makefile | 3 +
drivers/i2c/busses/i2c-virtio.c | 289
include/uapi/linux/virtio_i2c.h | 40 ++
include/uapi/linux/virtio_ids.h | 1 +
5 files changed, 344 insertions(+)
create mode 100644 drivers/i2c/busses/i2c-virtio.c
create mode 100644 include/uapi/linux/virtio_i2c.h
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 05ebf75..cb8d0d8 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -21,6 +21,17 @@ config I2C_ALI1535
This driver can also be built as a module. If so, the module
will be called i2c-ali1535.
+config I2C_VIRTIO
+ tristate "Virtio I2C Adapter"
+ select VIRTIO
+ help
+ If you say yes to this option, support will be included for the virtio
+ I2C adapter driver. The hardware can be emulated by any device model
+ software according to the virtio protocol.
+
+ This driver can also be built as a module. If so, the module
+ will be called i2c-virtio.
+
config I2C_ALI1563
tristate "ALI 1563"
depends on PCI
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 615f35e..efdd3f3 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -145,4 +145,7 @@ obj-$(CONFIG_I2C_XGENE_SLIMPRO) += i2c-xgene-slimpro.o
obj-$(CONFIG_SCx200_ACB) += scx200_acb.o
obj-$(CONFIG_I2C_FSI) += i2c-fsi.o
+# VIRTIO I2C host controller driver
+obj-$(CONFIG_I2C_VIRTIO) += i2c-virtio.o
+
ccflags-$(CONFIG_I2C_DEBUG_BUS) := -DDEBUG
diff --git a/drivers/i2c/busses/i2c-virtio.c b/drivers/i2c/busses/i2c-virtio.c
new file mode 100644
index 000..7a54bac
--- /dev/null
+++ b/drivers/i2c/busses/i2c-virtio.c
@@ -0,0 +1,289 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Virtio I2C Bus Driver
+ *
+ * The Virtio I2C Specification:
+ *
https://raw.githubusercontent.com/oasis-tcs/virtio-spec/master/virtio-i2c.tex
+ *
+ * Copyright (c) 2021 Intel Corporation. All rights reserved.
+ */
+
+#include
+#include
+#include
+#include
+#include
+#include
+#include
+#include
+#include
+#include
+
+/**
+ * struct virtio_i2c - virtio I2C data
+ * @vdev: virtio device for this controller
+ * @completion: completion of virtio I2C message
+ * @adap: I2C adapter for this controller
+ * @i2c_lock: lock for virtqueue processing
+ * @vq: the virtio virtqueue for communication
+ */
+struct virtio_i2c {
+ struct virtio_device *vdev;
+ struct completion completion;
+ struct i2c_adapter *adap;
+ struct mutex lock;
+ struct virtqueue *vq;
+};
+
+/**
+ * struct virtio_i2c_req - the virtio I2C request structure
+ * @out_hdr: the OUT header of the virtio I2C message
+ * @buf: the buffer into which data is read, or from which it's written
+ * @in_hdr: the IN header of the virtio I2C message
+ */
+struct virtio_i2c_req {
+ struct virtio_i2c_out_hdr out_hdr cacheline_aligned;
+ uint8_t *bufcacheline_aligned;
+ struct virtio_i2c_in_hdr in_hdr cacheline_aligned;
+};
+
+static void virtio_i2c_msg_done(struct virtqueue *vq)
+{
+ struct virtio_i2c *vi = vq->vdev->priv;
+
+ complete(>completion);
+}
+
+static int virtio_i2c_send_reqs(struct virtqueue *vq,
+ struct virtio_i2c_req *reqs,
+ struct i2c_msg *msgs, int nr)
+{
+ struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr;
+ int i, outcnt, incnt, err = 0;
+
+ for (i = 0; i < nr; i++) {
+ if (!msgs[i].len)
+ break;
+
+ /*
+* Only 7-bit mode supported for this moment. For the address
format,
+* Please check the Virtio I2C
