On 06/30/2015 07:24 AM, Archit Taneja wrote:
> mipi_dsi_devices are inherently aware of their host because they
> share a parent-child hierarchy in the device tree.
>
> Non-dsi drivers that create a dummy dsi device don't have this data.
> In order to get this information, they require to a phandle to the dsi
> host in the device tree.
>
> Maintain a list of all the hosts DSI that are currently registered.
>
> This list will be used to find the mipi_dsi_host corresponding to the
> device_node passed in of_find_mipi_dsi_host_by_node.
The lock protects only the list, there is no guarantee that mipi_dsi_host
returned by of_find_mipi_dsi_host_by_node is still valid, or will be valid long
enough.
But this issue affects many kernel frameworks so I am not sure if it should
block this
particular patch.
Reviewed-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
Regards
Andrzej
>
> Signed-off-by: Archit Taneja <architt@xxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_mipi_dsi.c | 30 ++++++++++++++++++++++++++++++
> include/drm/drm_mipi_dsi.h | 2 ++
> 2 files changed, 32 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
> index 9bfe215..81ddb73 100644
> --- a/drivers/gpu/drm/drm_mipi_dsi.c
> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
> @@ -239,6 +239,28 @@ struct mipi_dsi_device *mipi_dsi_new_dummy(struct mipi_dsi_host *host, u32 reg)
> return dsi;
> }
>
> +static DEFINE_MUTEX(host_lock);
> +static LIST_HEAD(host_list);
> +
> +struct mipi_dsi_host *of_find_mipi_dsi_host_by_node(struct device_node *node)
> +{
> + struct mipi_dsi_host *host;
> +
> + mutex_lock(&host_lock);
> +
> + list_for_each_entry(host, &host_list, list) {
> + if (host->dev->of_node == node) {
> + mutex_unlock(&host_lock);
> + return host;
> + }
> + }
> +
> + mutex_unlock(&host_lock);
> +
> + return NULL;
> +}
> +EXPORT_SYMBOL(of_find_mipi_dsi_host_by_node);
> +
> int mipi_dsi_host_register(struct mipi_dsi_host *host)
> {
> struct device_node *node;
> @@ -250,6 +272,10 @@ int mipi_dsi_host_register(struct mipi_dsi_host *host)
> of_mipi_dsi_device_add(host, node);
> }
>
> + mutex_lock(&host_lock);
> + list_add_tail(&host->list, &host_list);
> + mutex_unlock(&host_lock);
> +
> return 0;
> }
> EXPORT_SYMBOL(mipi_dsi_host_register);
> @@ -266,6 +292,10 @@ static int mipi_dsi_remove_device_fn(struct device *dev, void *priv)
> void mipi_dsi_host_unregister(struct mipi_dsi_host *host)
> {
> device_for_each_child(host->dev, NULL, mipi_dsi_remove_device_fn);
> +
> + mutex_lock(&host_lock);
> + list_del_init(&host->list);
> + mutex_unlock(&host_lock);
> }
> EXPORT_SYMBOL(mipi_dsi_host_unregister);
>
> diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
> index d06ba99..1684a0e 100644
> --- a/include/drm/drm_mipi_dsi.h
> +++ b/include/drm/drm_mipi_dsi.h
> @@ -100,10 +100,12 @@ struct mipi_dsi_host_ops {
> struct mipi_dsi_host {
> struct device *dev;
> const struct mipi_dsi_host_ops *ops;
> + struct list_head list;
> };
>
> int mipi_dsi_host_register(struct mipi_dsi_host *host);
> void mipi_dsi_host_unregister(struct mipi_dsi_host *host);
> +struct mipi_dsi_host *of_find_mipi_dsi_host_by_node(struct device_node *node);
>
> /* DSI mode flags */
>
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