Re: [PATCH 1/5] drm/vkms: Merge default_config and device

Sean Paul
2022-08-05T15:39:26Z

On Fri, Jul 22, 2022 at 05:32:09PM -0400, Jim Shargo wrote:
> This is a small refactor to make ConfigFS support easier.
>
> vkms_config is now a member of vkms_device and we now store a top-level
> reference to vkms_device.
>
> This should be a no-op refactor.
>
> Signed-off-by: Jim Shargo <jshargo@chromium.org>
> ---
> drivers/gpu/drm/vkms/vkms_drv.c | 58 +++++++++---------------------
> drivers/gpu/drm/vkms/vkms_drv.h | 5 ++-
> drivers/gpu/drm/vkms/vkms_output.c | 6 ++--
> 3 files changed, 22 insertions(+), 47 deletions(-)
>
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> index 0ffe5f0e33f7..81ed9417e511 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.c
> +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> @@ -37,7 +37,7 @@
> #define DRIVER_MAJOR 1
> #define DRIVER_MINOR 0
>
> -static struct vkms_config *default_config;
> +static struct vkms_device *vkms_device;

I think this should be stored in the platform device data on registration as
opposed to a global.

>
> static bool enable_cursor = true;
> module_param_named(enable_cursor, enable_cursor, bool, 0444);
> @@ -91,13 +91,9 @@ static void vkms_atomic_commit_tail(struct drm_atomic_state *old_state)
>
> static int vkms_config_show(struct seq_file *m, void *data)
> {
> - struct drm_info_node *node = (struct drm_info_node *)m->private;
> - struct drm_device *dev = node->minor->dev;
> - struct vkms_device *vkmsdev = drm_device_to_vkms_device(dev);
> -
> - seq_printf(m, "writeback=%d\n", vkmsdev->config->writeback);
> - seq_printf(m, "cursor=%d\n", vkmsdev->config->cursor);
> - seq_printf(m, "overlay=%d\n", vkmsdev->config->overlay);
> + seq_printf(m, "writeback=%d\n", vkms_device->config.writeback);
> + seq_printf(m, "cursor=%d\n", vkms_device->config.cursor);
> + seq_printf(m, "overlay=%d\n", vkms_device->config.overlay);
>
> return 0;
> }
> @@ -158,11 +154,10 @@ static int vkms_modeset_init(struct vkms_device *vkmsdev)
> return vkms_output_init(vkmsdev, 0);
> }
>
> -static int vkms_create(struct vkms_config *config)
> +static int vkms_create(void)
> {
> int ret;
> struct platform_device *pdev;
> - struct vkms_device *vkms_device;
>
> pdev = platform_device_register_simple(DRIVER_NAME, -1, NULL, 0);
> if (IS_ERR(pdev))
> @@ -179,9 +174,11 @@ static int vkms_create(struct vkms_config *config)
> ret = PTR_ERR(vkms_device);
> goto out_devres;
> }
> +

In order to avoid the vkms_device global you would call platform_set_drvdata()
here and use platform_get_drvdata() to retrieve it elsewhere.

> vkms_device->platform = pdev;
> - vkms_device->config = config;
> - config->dev = vkms_device;
> + vkms_device->config.cursor = enable_cursor;
> + vkms_device->config.writeback = enable_writeback;
> + vkms_device->config.overlay = enable_overlay;
>
> ret = dma_coerce_mask_and_coherent(vkms_device->drm.dev,
> DMA_BIT_MASK(64));
> @@ -207,6 +204,8 @@ static int vkms_create(struct vkms_config *config)
>
> drm_fbdev_generic_setup(&vkms_device->drm, 0);
>
> + vkms_device->initialized = true;
> +

Do we really need this? If so, is there a race between this and the check in vkms_exit(), or do you get serialization for free from module init/exit?

> return 0;
>
> out_devres:
> @@ -218,46 +217,23 @@ static int vkms_create(struct vkms_config *config)
>
> static int __init vkms_init(void)
> {
> - struct vkms_config *config;
> -
> - config = kmalloc(sizeof(*config), GFP_KERNEL);
> - if (!config)
> - return -ENOMEM;
> -
> - default_config = config;
> -
> - config->cursor = enable_cursor;
> - config->writeback = enable_writeback;
> - config->overlay = enable_overlay;
> -
> - return vkms_create(config);
> + return vkms_create();
> }
>
> -static void vkms_destroy(struct vkms_config *config)
> +static void __exit vkms_exit(void)
> {
> struct platform_device *pdev;
>
> - if (!config->dev) {
> - DRM_INFO("vkms_device is NULL.\n");
> + if (!vkms_device || !vkms_device->initialized) {
> return;
> }
>
> - pdev = config->dev->platform;
> + pdev = vkms_device->platform;
>
> - drm_dev_unregister(&config->dev->drm);
> - drm_atomic_helper_shutdown(&config->dev->drm);
> + drm_dev_unregister(&vkms_device->drm);
> + drm_atomic_helper_shutdown(&vkms_device->drm);
> devres_release_group(&pdev->dev, NULL);
> platform_device_unregister(pdev);
> -
> - config->dev = NULL;
> -}
> -
> -static void __exit vkms_exit(void)
> -{
> - if (default_config->dev)
> - vkms_destroy(default_config);
> -
> - kfree(default_config);
> }
>
> module_init(vkms_init);
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> index 91e63b12f60f..c7ebc4ee6b14 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.h
> +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> @@ -99,15 +99,14 @@ struct vkms_config {
> bool writeback;
> bool cursor;
> bool overlay;
> - /* only set when instantiated */
> - struct vkms_device *dev;
> };
>
> struct vkms_device {
> struct drm_device drm;
> struct platform_device *platform;
> struct vkms_output output;
> - const struct vkms_config *config;
> + struct vkms_config config;
> + bool initialized;
> };
>
> #define drm_crtc_to_vkms_output(target) \
> diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
> index ba0e82ae549a..d0061c82003a 100644
> --- a/drivers/gpu/drm/vkms/vkms_output.c
> +++ b/drivers/gpu/drm/vkms/vkms_output.c
> @@ -63,7 +63,7 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> if (IS_ERR(primary))
> return PTR_ERR(primary);
>
> - if (vkmsdev->config->overlay) {
> + if (vkmsdev->config.overlay) {
> for (n = 0; n < NUM_OVERLAY_PLANES; n++) {
> ret = vkms_add_overlay_plane(vkmsdev, index, crtc);
> if (ret)
> @@ -71,7 +71,7 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> }
> }
>
> - if (vkmsdev->config->cursor) {
> + if (vkmsdev->config.cursor) {
> cursor = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_CURSOR, index);
> if (IS_ERR(cursor))
> return PTR_ERR(cursor);
> @@ -103,7 +103,7 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
> goto err_attach;
> }
>
> - if (vkmsdev->config->writeback) {
> + if (vkmsdev->config.writeback) {
> writeback = vkms_enable_writeback_connector(vkmsdev);
> if (writeback)
> DRM_ERROR("Failed to init writeback connector\n");