[RFC PATCH v2 17/17] WIP: drm/tegra: Implement new UAPI

[Dmitry Osipenko]

05.09.2020 13:34, Mikko Perttunen пишет:
> +static int submit_process_bufs(struct drm_device *drm, struct gather_bo *bo,
> +			       struct tegra_drm_job_data *job_data,
> +			       struct tegra_drm_channel_ctx *ctx,
> +			       struct drm_tegra_channel_submit *args,
> +			       struct ww_acquire_ctx *acquire_ctx)
> +{
> +	struct drm_tegra_submit_buf __user *user_bufs_ptr =
> +		u64_to_user_ptr(args->bufs_ptr);

If assignment makes line too long, then factor it out.

  struct drm_tegra_submit_buf __user *user_bufs_ptr;

  user_bufs_ptr = u64_to_user_ptr(args->bufs_ptr);

> +	struct tegra_drm_mapping *mapping;
> +	struct drm_tegra_submit_buf buf;
> +	unsigned long copy_err;
> +	int err;
> +	u32 i;
> +
> +	job_data->used_mappings =
> +		kcalloc(args->num_bufs, sizeof(*job_data->used_mappings), GFP_KERNEL);

The checkpatch should disallow this coding style. I'd write it as:

size_t size;

size = sizeof(*job_data->used_mappings);
job_data->used_mappings = kcalloc(args->num_bufs, size..);

> +	if (!job_data->used_mappings)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < args->num_bufs; i++) {
> +		copy_err = copy_from_user(&buf, user_bufs_ptr+i, sizeof(buf));

Whole array always should be copied at once. Please keep in mind that
each copy_from_user() has a cpu-time cost, there should maximum up to 2
copyings per job.