linux-kernel - Re: [PATCH v16 09/20] drm/shmem-helper: Remove obsoleted is

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Message-ID: <b77955c6-b034-d0f0-f022-7c7523d7bef0@collabora.com>
Date:   Wed, 13 Sep 2023 03:06:33 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     Boris Brezillon <boris.brezillon@...labora.com>
Cc:     David Airlie <airlied@...il.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        Chia-I Wu <olvaffe@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Christian König <christian.koenig@....com>,
        Qiang Yu <yuq825@...il.com>,
        Steven Price <steven.price@....com>,
        Emma Anholt <emma@...olt.net>, Melissa Wen <mwen@...lia.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel@...labora.com, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v16 09/20] drm/shmem-helper: Remove obsoleted is_iomem
 test

On 9/5/23 09:46, Boris Brezillon wrote:
> On Sun,  3 Sep 2023 20:07:25 +0300
> Dmitry Osipenko <dmitry.osipenko@...labora.com> wrote:
> 
>> Everything that uses the mapped buffer should be agnostic to is_iomem.
>> The only reason for the is_iomem test is that we're setting shmem->vaddr
>> to the returned map->vaddr. Now that the shmem->vaddr code is gone, remove
>> the obsoleted is_iomem test to clean up the code.
>>
>> Suggested-by: Thomas Zimmermann <tzimmermann@...e.de>
>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
>> ---
>>  drivers/gpu/drm/drm_gem_shmem_helper.c | 6 ------
>>  1 file changed, 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> index 2b50d1a7f718..25e99468ced2 100644
>> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
>> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> @@ -317,12 +317,6 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
>>  
>>  	if (obj->import_attach) {
>>  		ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
>> -		if (!ret) {
>> -			if (drm_WARN_ON(obj->dev, map->is_iomem)) {
>> -				dma_buf_vunmap(obj->import_attach->dmabuf, map);
>> -				return -EIO;
>> -			}
>> -		}
> 
> Given there's nothing to unroll for the dmabuf case, I think it'd be
> good to return directly and skip all the error paths. It would also
> allow you to get rid of one indentation level for the !dmabuf path.
> 
> 	if (obj->import_attach)
> 		return dma_buf_vmap(obj->import_attach->dmabuf, map);
> 
> 	// non-dmabuf vmap logic here...

There is a common error message there that uses the common ret. The
error unwinding could be improved, but then it should be a separate
patch as it's unrelated to the change made here.

-- 
Best regards,
Dmitry