linux-kernel - Re: [PATCH v2] drm/shmem: Cleanup drm_gem_shmem_create_with

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Date:   Mon, 23 Jan 2023 14:31:52 +0000
From:   Steven Price <steven.price@....com>
To:     Rob Clark <robdclark@...il.com>, dri-devel@...ts.freedesktop.org
Cc:     Rob Clark <robdclark@...omium.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drm/shmem: Cleanup drm_gem_shmem_create_with_handle()

On 19/01/2023 22:44, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
> 
> Once we create the handle, the handle owns the reference.  Currently
> nothing was doing anything with the shmem ptr after the handle was
> created, but let's change drm_gem_shmem_create_with_handle() to not
> return the pointer, so-as to not encourage problematic use of this
> function in the future.  As a bonus, it makes the code a bit cleaner.
> 
> Signed-off-by: Rob Clark <robdclark@...omium.org>

Nice cleanup, one comment below:

> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index f21f47737817..fa6281e43954 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -415,7 +415,7 @@ void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem,
>  }
>  EXPORT_SYMBOL(drm_gem_shmem_vunmap);
>  
> -static struct drm_gem_shmem_object *
> +static int
>  drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
>  				 struct drm_device *dev, size_t size,
>  				 uint32_t *handle)
> @@ -425,7 +425,7 @@ drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
>  
>  	shmem = drm_gem_shmem_create(dev, size);
>  	if (IS_ERR(shmem))
> -		return shmem;
> +		return PTR_ERR(shmem);
>  
>  	/*
>  	 * Allocate an id of idr table where the obj is registered
> @@ -434,10 +434,8 @@ drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
>  	ret = drm_gem_handle_create(file_priv, &shmem->base, handle);
>  	/* drop reference from allocate - handle holds it now. */
>  	drm_gem_object_put(&shmem->base);
> -	if (ret)
> -		return ERR_PTR(ret);
>  
> -	return shmem;
> +	return ret;
>  }
>  
>  /* Update madvise status, returns true if not purged, else
> @@ -533,9 +531,7 @@ int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
>  			args->size = PAGE_ALIGN(args->pitch * args->height);
>  	}
>  
> -	shmem = drm_gem_shmem_create_with_handle(file, dev, args->size, &args->handle);

shmem is now unused in this function so the definition needs removing too.

Steve

> -
> -	return PTR_ERR_OR_ZERO(shmem);
> +	return drm_gem_shmem_create_with_handle(file, dev, args->size, &args->handle);
>  }
>  EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
>