Hi Javier,
Thank you for the patch.
On Mon, May 02, 2022 at 05:38:58PM +0200, Javier Martinez Canillas wrote:
> The drm_fbdev_generic_setup() function already sets the preferred bits per
> pixel for the device to dev->mode_config.preferred_depth, if preferred_bpp
> value is zero.
>
> Passing the same value to the function is unnecessary. Let's cleanup that
> in the two drivers that do it.
This looks fine, so
Reviewed-by: Laurent Pinchart <[email protected]>
but why do we have two different mechanisms to set the preferred depth ?
Could we get all drivers to set dev->mode_config.preferred_depth and
drop the depth option to drm_fbdev_generic_setup() ? There's a FIXME
comment in drm_fbdev_generic_setup() that could be related.
> Signed-off-by: Javier Martinez Canillas <[email protected]>
> Reviewed-by: Thomas Zimmermann <[email protected]>
> ---
>
> (no changes since v1)
>
> drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c | 2 +-
> drivers/gpu/drm/tiny/cirrus.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
> index fe4269c5aa0a..ace92459e462 100644
> --- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
> +++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
> @@ -349,7 +349,7 @@ static int hibmc_pci_probe(struct pci_dev *pdev,
> goto err_unload;
> }
>
> - drm_fbdev_generic_setup(dev, dev->mode_config.preferred_depth);
> + drm_fbdev_generic_setup(dev, 0);
>
> return 0;
>
> diff --git a/drivers/gpu/drm/tiny/cirrus.c b/drivers/gpu/drm/tiny/cirrus.c
> index c8e791840862..ed5a2e14894a 100644
> --- a/drivers/gpu/drm/tiny/cirrus.c
> +++ b/drivers/gpu/drm/tiny/cirrus.c
> @@ -601,7 +601,7 @@ static int cirrus_pci_probe(struct pci_dev *pdev,
> if (ret)
> return ret;
>
> - drm_fbdev_generic_setup(dev, dev->mode_config.preferred_depth);
> + drm_fbdev_generic_setup(dev, 0);
> return 0;
> }
>
--
Regards,
Laurent Pinchart
Hello Laurent,
On 5/2/22 18:06, Laurent Pinchart wrote:
> Hi Javier,
>
> Thank you for the patch.
>
> On Mon, May 02, 2022 at 05:38:58PM +0200, Javier Martinez Canillas wrote:
>> The drm_fbdev_generic_setup() function already sets the preferred bits per
>> pixel for the device to dev->mode_config.preferred_depth, if preferred_bpp
>> value is zero.
>>
>> Passing the same value to the function is unnecessary. Let's cleanup that
>> in the two drivers that do it.
>
> This looks fine, so
>
> Reviewed-by: Laurent Pinchart <[email protected]>
>
> but why do we have two different mechanisms to set the preferred depth ?
> Could we get all drivers to set dev->mode_config.preferred_depth and
Yes, that's the plan and the reason why when we were discussing with Thomas
about how to pass this option to the FB helper layer, we agreed on reusing
the @preferred_bpp parameter rather than adding a third parameter to
drm_fbdev_generic_setup(). Since in the future drivers shouldn't pass that
information to the FB helper and just get it from the default mode config.
But doing that would require more auditing to all drivers and it could add
regressions while patches 1/2 and 2/2 in this series shouldn't cause any
behavioral changes.
> drop the depth option to drm_fbdev_generic_setup() ? There's a FIXME
> comment in drm_fbdev_generic_setup() that could be related.
>
A FIXME makes sense, I'll add that to when posting a v3.
Best regards,
Javier Martinez Canillas
Linux Engineering
Red Hat
On 5/2/22 18:55, Javier Martinez Canillas wrote:
[snip]
>
>> drop the depth option to drm_fbdev_generic_setup() ? There's a FIXME
>> comment in drm_fbdev_generic_setup() that could be related.
>>
>
> A FIXME makes sense, I'll add that to when posting a v3.
There's actually a FIXME already in drm_fbdev_generic_setup(), so it's
a documented issue [0]:
void drm_fbdev_generic_setup(struct drm_device *dev,
unsigned int preferred_bpp)
{
...
/*
* FIXME: This mixes up depth with bpp, which results in a glorious
* mess, resulting in some drivers picking wrong fbdev defaults and
* others wrong preferred_depth defaults.
*/
if (!preferred_bpp)
preferred_bpp = dev->mode_config.preferred_depth;
if (!preferred_bpp)
preferred_bpp = 32;
fb_helper->preferred_bpp = preferred_bpp;
...
}
[0]: https://elixir.bootlin.com/linux/v5.18-rc5/source/drivers/gpu/drm/drm_fb_helper.c#L2553
--
Best regards,
Javier Martinez Canillas
Linux Engineering
Red Hat