question about drivers/gpu/drm/i915/dvo_ch7xxx.c
On Sat, Oct 06, 2012 at 03:20:19PM +0200, Julia Lawall wrote:
> Hello,
>
> I am looking at introducing some macros for i2c_msg initialization,
> and Ryan Mallon suggested that sometimes it could be useful to at
> the same time replace explicit lengths with the size of the
> associated buffer. But in some cases the sizes are not the same.
> An example is as follows, in drivers/gpu/drm/i915/dvo_ch7xxx.c:
>
> static bool ch7xxx_readb(struct intel_dvo_device *dvo, int addr,
> uint8_t *ch)
> {
> struct ch7xxx_priv *ch7xxx = dvo->dev_priv;
> struct i2c_adapter *adapter = dvo->i2c_bus;
> u8 out_buf[2];
> u8 in_buf[2];
>
> struct i2c_msg msgs[] = {
> {
> .addr = dvo->slave_addr,
> .flags = 0,
> .len = 1,
> .buf = out_buf,
> },
> {
> .addr = dvo->slave_addr,
> .flags = I2C_M_RD,
> .len = 1,
> .buf = in_buf,
> }
> };
>
> out_buf[0] = addr;
> out_buf[1] = 0;
>
> if (i2c_transfer(adapter, msgs, 2) == 2) {
> *ch = in_buf[0];
> return true;
> };
>
> if (!ch7xxx->quiet) {
> DRM_DEBUG_KMS("Unable to read register 0x%02x from
> %s:%02x.\n",
> addr, adapter->name, dvo->slave_addr);
> }
> return false;
> }
>
> The buffers both have size 2, but only one byte is asked to be read
> or written. Is there any need for the buffers to have size 2 in
> this case?
Looks like the 2 byte buffer size is just copy from writeb. And
didn't find any other reson for it not being just 1 byte.
> Unrelatedly, is it correct that ch has type uint8_t and out_buf and
> in_buf have type u8?
drm/i915 is totally confused about the (u)int*_t vs (s|t)* types
unfortunately. I think nowadays we mostly stick to _t typedefs, but not
consistenly.
Yours, Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
Re: question about drivers/gpu/drm/i915/dvo_ch7xxx.c
On Sat, Oct 06, 2012 at 03:20:19PM +0200, Julia Lawall wrote:
Hello,
I am looking at introducing some macros for i2c_msg initialization,
and Ryan Mallon suggested that sometimes it could be useful to at
the same time replace explicit lengths with the size of the
associated buffer. But in some cases the sizes are not the same.
An example is as follows, in drivers/gpu/drm/i915/dvo_ch7xxx.c:
static bool ch7xxx_readb(struct intel_dvo_device *dvo, int addr,
uint8_t *ch)
{
struct ch7xxx_priv *ch7xxx = dvo-dev_priv;
struct i2c_adapter *adapter = dvo-i2c_bus;
u8 out_buf[2];
u8 in_buf[2];
struct i2c_msg msgs[] = {
{
.addr = dvo-slave_addr,
.flags = 0,
.len = 1,
.buf = out_buf,
},
{
.addr = dvo-slave_addr,
.flags = I2C_M_RD,
.len = 1,
.buf = in_buf,
}
};
out_buf[0] = addr;
out_buf[1] = 0;
if (i2c_transfer(adapter, msgs, 2) == 2) {
*ch = in_buf[0];
return true;
};
if (!ch7xxx-quiet) {
DRM_DEBUG_KMS(Unable to read register 0x%02x from
%s:%02x.\n,
addr, adapter-name, dvo-slave_addr);
}
return false;
}
The buffers both have size 2, but only one byte is asked to be read
or written. Is there any need for the buffers to have size 2 in
this case?
Looks like the 2 byte buffer size is just copypasta from writeb. And
didn't find any other reson for it not being just 1 byte.
Unrelatedly, is it correct that ch has type uint8_t and out_buf and
in_buf have type u8?
drm/i915 is totally confused about the (u)int*_t vs (s|t)* types
unfortunately. I think nowadays we mostly stick to _t typedefs, but not
consistenly.
Yours, Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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question about drivers/gpu/drm/i915/dvo_ch7xxx.c
Hello,
I am looking at introducing some macros for i2c_msg initialization, and
Ryan Mallon suggested that sometimes it could be useful to at the same
time replace explicit lengths with the size of the associated buffer. But
in some cases the sizes are not the same. An example is as follows, in
drivers/gpu/drm/i915/dvo_ch7xxx.c:
static bool ch7xxx_readb(struct intel_dvo_device *dvo, int addr, uint8_t
*ch)
{
struct ch7xxx_priv *ch7xxx = dvo->dev_priv;
struct i2c_adapter *adapter = dvo->i2c_bus;
u8 out_buf[2];
u8 in_buf[2];
struct i2c_msg msgs[] = {
{
.addr = dvo->slave_addr,
.flags = 0,
.len = 1,
.buf = out_buf,
},
{
.addr = dvo->slave_addr,
.flags = I2C_M_RD,
.len = 1,
.buf = in_buf,
}
};
out_buf[0] = addr;
out_buf[1] = 0;
if (i2c_transfer(adapter, msgs, 2) == 2) {
*ch = in_buf[0];
return true;
};
if (!ch7xxx->quiet) {
DRM_DEBUG_KMS("Unable to read register 0x%02x from %s:%02x.\n",
addr, adapter->name, dvo->slave_addr);
}
return false;
}
The buffers both have size 2, but only one byte is asked to be read or
written. Is there any need for the buffers to have size 2 in this case?
Unrelatedly, is it correct that ch has type uint8_t and out_buf and in_buf
have type u8?
julia
question about drivers/gpu/drm/i915/dvo_ch7xxx.c
Hello,
I am looking at introducing some macros for i2c_msg initialization, and
Ryan Mallon suggested that sometimes it could be useful to at the same
time replace explicit lengths with the size of the associated buffer. But
in some cases the sizes are not the same. An example is as follows, in
drivers/gpu/drm/i915/dvo_ch7xxx.c:
static bool ch7xxx_readb(struct intel_dvo_device *dvo, int addr, uint8_t
*ch)
{
struct ch7xxx_priv *ch7xxx = dvo-dev_priv;
struct i2c_adapter *adapter = dvo-i2c_bus;
u8 out_buf[2];
u8 in_buf[2];
struct i2c_msg msgs[] = {
{
.addr = dvo-slave_addr,
.flags = 0,
.len = 1,
.buf = out_buf,
},
{
.addr = dvo-slave_addr,
.flags = I2C_M_RD,
.len = 1,
.buf = in_buf,
}
};
out_buf[0] = addr;
out_buf[1] = 0;
if (i2c_transfer(adapter, msgs, 2) == 2) {
*ch = in_buf[0];
return true;
};
if (!ch7xxx-quiet) {
DRM_DEBUG_KMS(Unable to read register 0x%02x from %s:%02x.\n,
addr, adapter-name, dvo-slave_addr);
}
return false;
}
The buffers both have size 2, but only one byte is asked to be read or
written. Is there any need for the buffers to have size 2 in this case?
Unrelatedly, is it correct that ch has type uint8_t and out_buf and in_buf
have type u8?
julia
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