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

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Message-ID: <20230905084611.6a404ff1@collabora.com>
Date:   Tue, 5 Sep 2023 08:46:11 +0200
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Dmitry Osipenko <dmitry.osipenko@...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 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...



>  	} else {
>  		pgprot_t prot = PAGE_KERNEL;
>