linux-kernel - Re: [PATCH] drm/loongson: Remove a useless check in cursor_plane_atomic_async

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Date:   Mon, 10 Jul 2023 13:51:38 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     suijingfeng <suijingfeng@...ngson.cn>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, Li Yi <liyi@...ngson.cn>
Cc:     loongson-kernel@...ts.loongnix.cn,
        Dan Carpenter <dan.carpenter@...aro.org>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/loongson: Remove a useless check in
 cursor_plane_atomic_async_check()

Hi

Am 10.07.23 um 13:34 schrieb suijingfeng:
> Hi,
> 
> On 2023/7/10 18:39, Thomas Zimmermann wrote:
>>
>>
>> Am 10.07.23 um 12:24 schrieb Sui Jingfeng:
>>> Because smatch warnings:
>>>
>>> drivers/gpu/drm/loongson/lsdc_plane.c:199
>>> lsdc_cursor_plane_atomic_async_check()
>>> warn: variable dereferenced before check 'state' (see line 180)
>>>
>>> vim +/state +199 drivers/gpu/drm/loongson/lsdc_plane.c
>>>
>>> 174  static int
>>>       lsdc_cursor_plane_atomic_async_check(struct drm_plane *plane,
>>> 175                                       struct drm_atomic_state 
>>> *state)
>>> 176  {
>>> 177          struct drm_plane_state *new_state;
>>> 178          struct drm_crtc_state *crtc_state;
>>> 179
>>> 180          new_state = drm_atomic_get_new_plane_state(state, plane);
>>>                                                          ^^^^^
>>> state is dereferenced inside this function
>>>
>>> 181
>>> 182  if (!plane->state || !plane->state->fb) {
>>> 183          drm_dbg(plane->dev, "%s: state is NULL\n", plane->name);
>>> 184                  return -EINVAL;
>>> 185  }
>>> 186
>>> 187  if (new_state->crtc_w != new_state->crtc_h) {
>>> 188          drm_dbg(plane->dev, "unsupported cursor size: %ux%u\n",
>>> 189                  new_state->crtc_w, new_state->crtc_h);
>>> 190          return -EINVAL;
>>> 191  }
>>> 192
>>> 193  if (new_state->crtc_w != 64 && new_state->crtc_w != 32) {
>>> 194          drm_dbg(plane->dev, "unsupported cursor size: %ux%u\n",
>>> 195                  new_state->crtc_w, new_state->crtc_h);
>>> 196          return -EINVAL;
>>> 197  }
>>> 198
>>> 199  if (state) {
>>>           ^^^^^
>>> Checked too late!
>>>
>>> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
>>> Closes: https://lore.kernel.org/r/202307100423.rV7D05Uq-lkp@intel.com/
>>> Signed-off-by: Sui Jingfeng <suijingfeng@...ngson.cn>
>>
>> Acked-by: Thomas Zimmermann <tzimmermann@...e.de>
>>
>> BTW, you're posting these patches for loongson, 
> 
> I'm posting these patches for the drm/loongson driver in drm-misc and/or 
> drm-tip branch,
> 
> what do you means for *loongson*,
> 
>> but that driver is not yet in our tree?
>>
> 
> I already applied(push) drm/loongson driver to drm-misc-next branch,
> 
> What do you means that by "not yet in our tree", linux kernel side?
> 
> Am I missing something ?

No, it's my fault. I didn't update my branches correctly. :)

Best regards
Thomas

> 
> 
>> Best regards
>> Thomas
>>
>>
>>> ---
>>>   drivers/gpu/drm/loongson/lsdc_plane.c | 8 +-------
>>>   1 file changed, 1 insertion(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/loongson/lsdc_plane.c 
>>> b/drivers/gpu/drm/loongson/lsdc_plane.c
>>> index 2ab3db982aa3..0d5094633222 100644
>>> --- a/drivers/gpu/drm/loongson/lsdc_plane.c
>>> +++ b/drivers/gpu/drm/loongson/lsdc_plane.c
>>> @@ -196,13 +196,7 @@ static int 
>>> lsdc_cursor_plane_atomic_async_check(struct drm_plane *plane,
>>>           return -EINVAL;
>>>       }
>>>   -    if (state) {
>>> -        crtc_state = drm_atomic_get_existing_crtc_state(state, 
>>> new_state->crtc);
>>> -    } else {
>>> -        crtc_state = plane->crtc->state;
>>> -        drm_dbg(plane->dev, "%s: atomic state is NULL\n", plane->name);
>>> -    }
>>> -
>>> +    crtc_state = drm_atomic_get_existing_crtc_state(state, 
>>> new_state->crtc);
>>>       if (!crtc_state->active)
>>>           return -EINVAL;
>>
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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