Re: [Intel-gfx] [PATCH 15/44] drm/udl: Use demv_drm_dev_alloc

["Noralf Trønnes" <noralf@tronnes.org>]

Den 05.04.2020 15.47, skrev Daniel Vetter:
> On Sun, Apr 5, 2020 at 12:18 PM Noralf Trønnes <noralf@tronnes.org> wrote:
>>
>>
>>
>> Den 03.04.2020 15.57, skrev Daniel Vetter:
>>> Also init the fbdev emulation before we register the device, that way
>>> we can rely on the auto-cleanup and simplify the probe error code even
>>> more.
>>>
>>> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
>>> Cc: Dave Airlie <airlied@redhat.com>
>>> Cc: Sean Paul <sean@poorly.run>
>>> Cc: Thomas Zimmermann <tzimmermann@suse.de>
>>> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
>>> Cc: Emil Velikov <emil.l.velikov@gmail.com>
>>> Cc: Sam Ravnborg <sam@ravnborg.org>
>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>> ---
>>>  drivers/gpu/drm/udl/udl_drv.c | 36 +++++++++++------------------------
>>>  1 file changed, 11 insertions(+), 25 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c
>>> index 1ce2d865c36d..4ba5149fdd57 100644
>>> --- a/drivers/gpu/drm/udl/udl_drv.c
>>> +++ b/drivers/gpu/drm/udl/udl_drv.c
>>> @@ -57,27 +57,20 @@ static struct udl_device *udl_driver_create(struct usb_interface *interface)
>>>       struct udl_device *udl;
>>>       int r;
>>>
>>> -     udl = kzalloc(sizeof(*udl), GFP_KERNEL);
>>> -     if (!udl)
>>> -             return ERR_PTR(-ENOMEM);
>>> -
>>> -     r = drm_dev_init(&udl->drm, &driver, &interface->dev);
>>> -     if (r) {
>>> -             kfree(udl);
>>> -             return ERR_PTR(r);
>>> -     }
>>> +     udl = devm_drm_dev_alloc(&interface->dev, &driver,
>>> +                              struct udl_device, drm);
>>> +     if (IS_ERR(udl))
>>> +             return udl;
>>>
>>>       udl->udev = udev;
>>>       udl->drm.dev_private = udl;
>>> -     drmm_add_final_kfree(&udl->drm, udl);
>>>
>>>       r = udl_init(udl);
>>> -     if (r) {
>>> -             drm_dev_put(&udl->drm);
>>> +     if (r)
>>>               return ERR_PTR(r);
>>> -     }
>>>
>>>       usb_set_intfdata(interface, udl);
>>> +
>>>       return udl;
>>>  }
>>>
>>> @@ -91,23 +84,17 @@ static int udl_usb_probe(struct usb_interface *interface,
>>>       if (IS_ERR(udl))
>>>               return PTR_ERR(udl);
>>>
>>> +     r = drm_fbdev_generic_setup(&udl->drm, 0);
>>
>> It doesn't feel right to have a client open the device before the DRM
>> device itself is registered. I would prefer to keep it where it is but
>> ignore any errors. A failing client shouldn't prevent the driver from
>> probing. drm_fbdev_generic_setup() do print errors if it fails. So yeah,
>> in hindsight I should have made drm_fbdev_generic_setup() return void.
> 
> Hm, we have all kinds of usage right now, some check for errors, some
> dont, some do this before drm_dev_register, some after. If your
> recommendation is to not check for errors then I'm happy to implement
> that, but we're a bit inconsistent. Maybe we should do a patch that at
> least always returns 0 no matter what, plus document that the return
> value  shouldn't be checked?

Yeah, always returning zero and documenting it would be a good start.

I counted 41 drivers using generic fbdev now, didn't know it was that
much used. Only 11 drivers are hand rolling their own:
armada
gma500
amd
omapdrm
nouveau
i915
msm
tegra
exynos
radeon
rockchip

Noralf.
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