[Intel-gfx] [PATCH] Check if the bus is valid prior to discovering edid.

[Dave Airlie]

On Thu, Oct 13, 2011 at 9:36 PM, Eugeni Dodonov <eugeni at dodonov.net> wrote:
> On Thu, Oct 13, 2011 at 17:34, Adam Jackson <ajax at redhat.com> wrote:
>>
>> On Thu, 2011-10-13 at 15:11 -0300, Eugeni Dodonov wrote:
>>
>> > diff --git a/drivers/gpu/drm/i915/intel_i2c.c
>> > b/drivers/gpu/drm/i915/intel_i2c.c
>> > index d98cee6..b3a6eda 100644
>> > --- a/drivers/gpu/drm/i915/intel_i2c.c
>> > +++ b/drivers/gpu/drm/i915/intel_i2c.c
>> > @@ -470,3 +470,45 @@ void intel_teardown_gmbus(struct drm_device *dev)
>> >       kfree(dev_priv->gmbus);
>> >       dev_priv->gmbus = NULL;
>> >  }
>> > +
>> > +/**
>> > + * intel_drm_get_valid_edid - gets edid from existent adapters only
>> > + * @connector: DRM connector device to use
>> > + * @adapter: i2c adapter
>> > + *
>> > + * Verifies if the i2c adapter is responding to our queries before
>> > + * attempting to do proper communication with it. If it does,
>> > + * retreive the EDID with help of drm_get_edid
>> > + */
>> > +struct edid *
>> > +intel_drm_get_valid_edid(struct drm_connector *connector,
>> > +             struct i2c_adapter *adapter)
>> > +{
>> > +     int ret;
>> > +     u8 out_buf[] = { 0x0, 0x0};
>> > +     u8 buf[2];
>> > +     struct i2c_msg msgs[] = {
>> > +             {
>> > +                     .addr = 0x50,
>> > +                     .flags = 0,
>> > +                     .len = 1,
>> > +                     .buf = out_buf,
>> > +             },
>> > +             {
>> > +                     .addr = 0x50,
>> > +                     .flags = I2C_M_RD,
>> > +                     .len = 1,
>> > +                     .buf = buf,
>> > +             }
>> > +     };
>> > +
>> > +     /* We just check for -ENXIO - drm_get_edid checks if the transfer
>> > +      * works and manages the remaining parts of the EDID */
>> > +     ret = i2c_transfer(adapter, msgs, 2);
>>
>> This seems like it should be the implementation body of drm_probe_ddc,
>> and like that function should be EXPORT_SYMBOL()'d.  Other people want
>> to do zero-length reads too, you know.
>>
>> - ajax
>
> My other patch in the previous series
> (http://www.mail-archive.com/intel-gfx@lists.freedesktop.org/msg05828.html)
> did exactly that, but it haven't received any comments, and there was one
> report saying that it decreased the detection timing on a radeon card. I
> don't have any to test, so I prefer to focus on Intel ones (which I have)
> :).


Thats not how we develop in the kernel btw.

You should go around trying to poke developers from other drivers to
test the patch.

Dave.