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

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Message-ID: <8182fecd-d290-293a-d963-ddbea79dbf03@loongson.cn>
Date:   Mon, 10 Jul 2023 19:34:28 +0800
From:   suijingfeng <suijingfeng@...ngson.cn>
To:     Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, Li Yi <liyi@...ngson.cn>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        loongson-kernel@...ts.loongnix.cn,
        Dan Carpenter <dan.carpenter@...aro.org>
Subject: Re: [PATCH] drm/loongson: Remove a useless check in
 cursor_plane_atomic_async_check()

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 ?


> 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;
>