Re: [PATCH 1/6] usb: Iterator for ports
On Thu, Mar 25, 2021 at 04:20:15PM +0100, Greg Kroah-Hartman wrote:
> On Thu, Mar 25, 2021 at 05:14:42PM +0200, Heikki Krogerus wrote:
> > On Thu, Mar 25, 2021 at 10:41:09AM -0400, Alan Stern wrote:
> > > On Thu, Mar 25, 2021 at 03:29:21PM +0300, Heikki Krogerus wrote:
> > > > Introducing usb_for_each_port(). It works the same way as
> > > > usb_for_each_dev(), but instead of going through every USB
> > > > device in the system, it walks through the USB ports in the
> > > > system.
> > > >
> > > > Signed-off-by: Heikki Krogerus
> > >
> > > This has a couple of nasty errors.
> > >
> > > > ---
> > > > drivers/usb/core/usb.c | 43 ++
> > > > include/linux/usb.h| 1 +
> > > > 2 files changed, 44 insertions(+)
> > > >
> > > > diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
> > > > index 2ce3667ec6fae..6d49db9a1b208 100644
> > > > --- a/drivers/usb/core/usb.c
> > > > +++ b/drivers/usb/core/usb.c
> > > > @@ -398,6 +398,49 @@ int usb_for_each_dev(void *data, int (*fn)(struct
> > > > usb_device *, void *))
> > > > }
> > > > EXPORT_SYMBOL_GPL(usb_for_each_dev);
> > > >
> > > > +struct each_hub_arg {
> > > > + void *data;
> > > > + int (*fn)(struct device *, void *);
> > > > +};
> > > > +
> > > > +static int __each_hub(struct device *dev, void *data)
> > > > +{
> > > > + struct each_hub_arg *arg = (struct each_hub_arg *)data;
> > > > + struct usb_device *hdev = to_usb_device(dev);
> > >
> > > to_usb_device() won't work properly if the struct device isn't embedded
> > > in an actual usb_device structure. And that will happen, since the USB
> > > bus type holds usb_interface structures as well as usb_devices.
> >
> > OK, so I need to filter them out.
> >
> > > In fact, you should use usb_for_each_dev here; it already does what you
> > > want.
> >
> > Unfortunately I can't use usb_for_each_dev here, because it deals with
> > struct usb_device while I need to deal with struct device in the
> > callback.
>
> Why do you need 'struct device' in the callback? All you really want is
> the hub devices, right?
I need the ports, not the hubs.
> > > > + struct usb_hub *hub;
> > > > + int ret;
> > > > + int i;
> > > > +
> > > > + hub = usb_hub_to_struct_hub(hdev);
> > > > + if (!hub)
> > > > + return 0;
> > > > +
> > > > + for (i = 0; i < hdev->maxchild; i++) {
> > > > + ret = arg->fn(>ports[i]->dev, arg->data);
> > > > + if (ret)
> > > > + return ret;
> > > > + }
> > > > +
> > > > + return 0;
> > > > +}
> > >
> > > Don't you need some sort of locking or refcounting here? What would
> > > happen if this hub got removed while the routine was running?
> >
> > I'll use a lock then.
>
> That's not going to work to be held over a callback. Just properly
> increment the reference count.
I though we have done that already. Does bus_for_each_dev() do that
for the device that it passes to the callback until that callback
returns?
thanks,
--
heikki
Re: [PATCH 1/6] usb: Iterator for ports
On Thu, Mar 25, 2021 at 05:14:42PM +0200, Heikki Krogerus wrote:
> On Thu, Mar 25, 2021 at 10:41:09AM -0400, Alan Stern wrote:
> > On Thu, Mar 25, 2021 at 03:29:21PM +0300, Heikki Krogerus wrote:
> > > Introducing usb_for_each_port(). It works the same way as
> > > usb_for_each_dev(), but instead of going through every USB
> > > device in the system, it walks through the USB ports in the
> > > system.
> > >
> > > Signed-off-by: Heikki Krogerus
> >
> > This has a couple of nasty errors.
> >
> > > ---
> > > drivers/usb/core/usb.c | 43 ++
> > > include/linux/usb.h| 1 +
> > > 2 files changed, 44 insertions(+)
> > >
> > > diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
> > > index 2ce3667ec6fae..6d49db9a1b208 100644
> > > --- a/drivers/usb/core/usb.c
> > > +++ b/drivers/usb/core/usb.c
> > > @@ -398,6 +398,49 @@ int usb_for_each_dev(void *data, int (*fn)(struct
> > > usb_device *, void *))
> > > }
> > > EXPORT_SYMBOL_GPL(usb_for_each_dev);
> > >
> > > +struct each_hub_arg {
> > > + void *data;
> > > + int (*fn)(struct device *, void *);
> > > +};
> > > +
> > > +static int __each_hub(struct device *dev, void *data)
> > > +{
> > > + struct each_hub_arg *arg = (struct each_hub_arg *)data;
> > > + struct usb_device *hdev = to_usb_device(dev);
> >
> > to_usb_device() won't work properly if the struct device isn't embedded
> > in an actual usb_device structure. And that will happen, since the USB
> > bus type holds usb_interface structures as well as usb_devices.
>
> OK, so I need to filter them out.
>
> > In fact, you should use usb_for_each_dev here; it already does what you
> > want.
>
> Unfortunately I can't use usb_for_each_dev here, because it deals with
> struct usb_device while I need to deal with struct device in the
> callback.
I see; the prototypes of arg->fn are different. Oh well, it's a shame
the code can't be reused. In any case, you should copy what
usb.c:__each_dev() does.
Alan Stern
> > > + struct usb_hub *hub;
> > > + int ret;
> > > + int i;
> > > +
> > > + hub = usb_hub_to_struct_hub(hdev);
> > > + if (!hub)
> > > + return 0;
> > > +
> > > + for (i = 0; i < hdev->maxchild; i++) {
> > > + ret = arg->fn(>ports[i]->dev, arg->data);
> > > + if (ret)
> > > + return ret;
> > > + }
> > > +
> > > + return 0;
> > > +}
> >
> > Don't you need some sort of locking or refcounting here? What would
> > happen if this hub got removed while the routine was running?
>
> I'll use a lock then.
>
> thanks,
>
> --
> heikki
Re: [PATCH 1/6] usb: Iterator for ports
On Thu, Mar 25, 2021 at 05:14:45PM +0200, Heikki Krogerus wrote:
> On Thu, Mar 25, 2021 at 10:41:09AM -0400, Alan Stern wrote:
> > On Thu, Mar 25, 2021 at 03:29:21PM +0300, Heikki Krogerus wrote:
> > > Introducing usb_for_each_port(). It works the same way as
> > > usb_for_each_dev(), but instead of going through every USB
> > > device in the system, it walks through the USB ports in the
> > > system.
> > >
> > > Signed-off-by: Heikki Krogerus
> >
> > This has a couple of nasty errors.
> >
> > > ---
> > > drivers/usb/core/usb.c | 43 ++
> > > include/linux/usb.h| 1 +
> > > 2 files changed, 44 insertions(+)
> > >
> > > diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
> > > index 2ce3667ec6fae..6d49db9a1b208 100644
> > > --- a/drivers/usb/core/usb.c
> > > +++ b/drivers/usb/core/usb.c
> > > @@ -398,6 +398,49 @@ int usb_for_each_dev(void *data, int (*fn)(struct
> > > usb_device *, void *))
> > > }
> > > EXPORT_SYMBOL_GPL(usb_for_each_dev);
> > >
> > > +struct each_hub_arg {
> > > + void *data;
> > > + int (*fn)(struct device *, void *);
> > > +};
> > > +
> > > +static int __each_hub(struct device *dev, void *data)
> > > +{
> > > + struct each_hub_arg *arg = (struct each_hub_arg *)data;
> > > + struct usb_device *hdev = to_usb_device(dev);
> >
> > to_usb_device() won't work properly if the struct device isn't embedded
> > in an actual usb_device structure. And that will happen, since the USB
> > bus type holds usb_interface structures as well as usb_devices.
>
> OK, so I need to filter them out.
>
> > In fact, you should use usb_for_each_dev here; it already does what you
> > want.
>
> Unfortunately I can't use usb_for_each_dev here, because it deals with
> struct usb_device while I need to deal with struct device in the
> callback.
Ah, I can use it instead of bus_for_each_dev() in usb_for_each_port().
I'll fix these in v2.
For the lock I guess I can just use the peer lock (usb_port_peer_mutex)?
thanks,
--
heikki
Re: [PATCH 1/6] usb: Iterator for ports
On Thu, Mar 25, 2021 at 05:14:42PM +0200, Heikki Krogerus wrote:
> On Thu, Mar 25, 2021 at 10:41:09AM -0400, Alan Stern wrote:
> > On Thu, Mar 25, 2021 at 03:29:21PM +0300, Heikki Krogerus wrote:
> > > Introducing usb_for_each_port(). It works the same way as
> > > usb_for_each_dev(), but instead of going through every USB
> > > device in the system, it walks through the USB ports in the
> > > system.
> > >
> > > Signed-off-by: Heikki Krogerus
> >
> > This has a couple of nasty errors.
> >
> > > ---
> > > drivers/usb/core/usb.c | 43 ++
> > > include/linux/usb.h| 1 +
> > > 2 files changed, 44 insertions(+)
> > >
> > > diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
> > > index 2ce3667ec6fae..6d49db9a1b208 100644
> > > --- a/drivers/usb/core/usb.c
> > > +++ b/drivers/usb/core/usb.c
> > > @@ -398,6 +398,49 @@ int usb_for_each_dev(void *data, int (*fn)(struct
> > > usb_device *, void *))
> > > }
> > > EXPORT_SYMBOL_GPL(usb_for_each_dev);
> > >
> > > +struct each_hub_arg {
> > > + void *data;
> > > + int (*fn)(struct device *, void *);
> > > +};
> > > +
> > > +static int __each_hub(struct device *dev, void *data)
> > > +{
> > > + struct each_hub_arg *arg = (struct each_hub_arg *)data;
> > > + struct usb_device *hdev = to_usb_device(dev);
> >
> > to_usb_device() won't work properly if the struct device isn't embedded
> > in an actual usb_device structure. And that will happen, since the USB
> > bus type holds usb_interface structures as well as usb_devices.
>
> OK, so I need to filter them out.
>
> > In fact, you should use usb_for_each_dev here; it already does what you
> > want.
>
> Unfortunately I can't use usb_for_each_dev here, because it deals with
> struct usb_device while I need to deal with struct device in the
> callback.
Why do you need 'struct device' in the callback? All you really want is
the hub devices, right?
> > > + struct usb_hub *hub;
> > > + int ret;
> > > + int i;
> > > +
> > > + hub = usb_hub_to_struct_hub(hdev);
> > > + if (!hub)
> > > + return 0;
> > > +
> > > + for (i = 0; i < hdev->maxchild; i++) {
> > > + ret = arg->fn(>ports[i]->dev, arg->data);
> > > + if (ret)
> > > + return ret;
> > > + }
> > > +
> > > + return 0;
> > > +}
> >
> > Don't you need some sort of locking or refcounting here? What would
> > happen if this hub got removed while the routine was running?
>
> I'll use a lock then.
That's not going to work to be held over a callback. Just properly
increment the reference count.
thanks,
greg k-h
Re: [PATCH 1/6] usb: Iterator for ports
On Thu, Mar 25, 2021 at 10:41:09AM -0400, Alan Stern wrote:
> On Thu, Mar 25, 2021 at 03:29:21PM +0300, Heikki Krogerus wrote:
> > Introducing usb_for_each_port(). It works the same way as
> > usb_for_each_dev(), but instead of going through every USB
> > device in the system, it walks through the USB ports in the
> > system.
> >
> > Signed-off-by: Heikki Krogerus
>
> This has a couple of nasty errors.
>
> > ---
> > drivers/usb/core/usb.c | 43 ++
> > include/linux/usb.h| 1 +
> > 2 files changed, 44 insertions(+)
> >
> > diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
> > index 2ce3667ec6fae..6d49db9a1b208 100644
> > --- a/drivers/usb/core/usb.c
> > +++ b/drivers/usb/core/usb.c
> > @@ -398,6 +398,49 @@ int usb_for_each_dev(void *data, int (*fn)(struct
> > usb_device *, void *))
> > }
> > EXPORT_SYMBOL_GPL(usb_for_each_dev);
> >
> > +struct each_hub_arg {
> > + void *data;
> > + int (*fn)(struct device *, void *);
> > +};
> > +
> > +static int __each_hub(struct device *dev, void *data)
> > +{
> > + struct each_hub_arg *arg = (struct each_hub_arg *)data;
> > + struct usb_device *hdev = to_usb_device(dev);
>
> to_usb_device() won't work properly if the struct device isn't embedded
> in an actual usb_device structure. And that will happen, since the USB
> bus type holds usb_interface structures as well as usb_devices.
OK, so I need to filter them out.
> In fact, you should use usb_for_each_dev here; it already does what you
> want.
Unfortunately I can't use usb_for_each_dev here, because it deals with
struct usb_device while I need to deal with struct device in the
callback.
> > + struct usb_hub *hub;
> > + int ret;
> > + int i;
> > +
> > + hub = usb_hub_to_struct_hub(hdev);
> > + if (!hub)
> > + return 0;
> > +
> > + for (i = 0; i < hdev->maxchild; i++) {
> > + ret = arg->fn(>ports[i]->dev, arg->data);
> > + if (ret)
> > + return ret;
> > + }
> > +
> > + return 0;
> > +}
>
> Don't you need some sort of locking or refcounting here? What would
> happen if this hub got removed while the routine was running?
I'll use a lock then.
thanks,
--
heikki
Re: [PATCH 1/6] usb: Iterator for ports
On Thu, Mar 25, 2021 at 03:29:21PM +0300, Heikki Krogerus wrote:
> Introducing usb_for_each_port(). It works the same way as
> usb_for_each_dev(), but instead of going through every USB
> device in the system, it walks through the USB ports in the
> system.
>
> Signed-off-by: Heikki Krogerus
This has a couple of nasty errors.
> ---
> drivers/usb/core/usb.c | 43 ++
> include/linux/usb.h| 1 +
> 2 files changed, 44 insertions(+)
>
> diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
> index 2ce3667ec6fae..6d49db9a1b208 100644
> --- a/drivers/usb/core/usb.c
> +++ b/drivers/usb/core/usb.c
> @@ -398,6 +398,49 @@ int usb_for_each_dev(void *data, int (*fn)(struct
> usb_device *, void *))
> }
> EXPORT_SYMBOL_GPL(usb_for_each_dev);
>
> +struct each_hub_arg {
> + void *data;
> + int (*fn)(struct device *, void *);
> +};
> +
> +static int __each_hub(struct device *dev, void *data)
> +{
> + struct each_hub_arg *arg = (struct each_hub_arg *)data;
> + struct usb_device *hdev = to_usb_device(dev);
to_usb_device() won't work properly if the struct device isn't embedded
in an actual usb_device structure. And that will happen, since the USB
bus type holds usb_interface structures as well as usb_devices.
In fact, you should use usb_for_each_dev here; it already does what you
want.
> + struct usb_hub *hub;
> + int ret;
> + int i;
> +
> + hub = usb_hub_to_struct_hub(hdev);
> + if (!hub)
> + return 0;
> +
> + for (i = 0; i < hdev->maxchild; i++) {
> + ret = arg->fn(>ports[i]->dev, arg->data);
> + if (ret)
> + return ret;
> + }
> +
> + return 0;
> +}
Don't you need some sort of locking or refcounting here? What would
happen if this hub got removed while the routine was running?
Alan Stern
[PATCH 1/6] usb: Iterator for ports
Introducing usb_for_each_port(). It works the same way as
usb_for_each_dev(), but instead of going through every USB
device in the system, it walks through the USB ports in the
system.
Signed-off-by: Heikki Krogerus
---
drivers/usb/core/usb.c | 43 ++
include/linux/usb.h| 1 +
2 files changed, 44 insertions(+)
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 2ce3667ec6fae..6d49db9a1b208 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -398,6 +398,49 @@ int usb_for_each_dev(void *data, int (*fn)(struct
usb_device *, void *))
}
EXPORT_SYMBOL_GPL(usb_for_each_dev);
+struct each_hub_arg {
+ void *data;
+ int (*fn)(struct device *, void *);
+};
+
+static int __each_hub(struct device *dev, void *data)
+{
+ struct each_hub_arg *arg = (struct each_hub_arg *)data;
+ struct usb_device *hdev = to_usb_device(dev);
+ struct usb_hub *hub;
+ int ret;
+ int i;
+
+ hub = usb_hub_to_struct_hub(hdev);
+ if (!hub)
+ return 0;
+
+ for (i = 0; i < hdev->maxchild; i++) {
+ ret = arg->fn(>ports[i]->dev, arg->data);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+
+/**
+ * usb_for_each_port - interate over all USB ports in the system
+ * @data: data pointer that will be handed to the callback function
+ * @fn: callback function to be called for each USB port
+ *
+ * Iterate over all USB ports and call @fn for each, passing it @data. If it
+ * returns anything other than 0, we break the iteration prematurely and return
+ * that value.
+ */
+int usb_for_each_port(void *data, int (*fn)(struct device *, void *))
+{
+ struct each_hub_arg arg = {data, fn};
+
+ return bus_for_each_dev(_bus_type, NULL, , __each_hub);
+}
+EXPORT_SYMBOL_GPL(usb_for_each_port);
+
/**
* usb_release_dev - free a usb device structure when all users of it are
finished.
* @dev: device that's been disconnected
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 57c1e0ce5eba4..06ed5779fb4d8 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -869,6 +869,7 @@ extern int usb_match_one_id(struct usb_interface *interface,
const struct usb_device_id *id);
extern int usb_for_each_dev(void *data, int (*fn)(struct usb_device *, void
*));
+int usb_for_each_port(void *data, int (*fn)(struct device *, void *));
extern struct usb_interface *usb_find_interface(struct usb_driver *drv,
int minor);
extern struct usb_interface *usb_ifnum_to_if(const struct usb_device *dev,
--
2.30.2
