Re: [PATCH] staging: bcm2835-camera: Replace open-coded idr with a struct idr.

[Stefan Wahren]

Hi Eric,

> Eric Anholt <eric@xxxxxxxxxx> hat am 11. Mai 2018 um 01:31 geschrieben:
> 
> 
> We just need some integer handles that can map back to our message
> struct when we're handling a reply, which struct idr is perfect for.
> 
> Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>
> ---
>  .../vc04_services/bcm2835-camera/mmal-vchiq.c | 135 ++++--------------
>  1 file changed, 31 insertions(+), 104 deletions(-)
> 
> diff --git a/drivers/staging/vc04_services/bcm2835-camera/mmal-vchiq.c b/drivers/staging/vc04_services/bcm2835-camera/mmal-vchiq.c
> index 3a3b843fc122..f0dac6440cfb 100644
> --- a/drivers/staging/vc04_services/bcm2835-camera/mmal-vchiq.c
> +++ b/drivers/staging/vc04_services/bcm2835-camera/mmal-vchiq.c
> @@ -21,7 +21,6 @@
>  #include <linux/slab.h>
>  #include <linux/completion.h>
>  #include <linux/vmalloc.h>
> -#include <linux/btree.h>
>  #include <asm/cacheflush.h>
>  #include <media/videobuf2-vmalloc.h>
>  
> @@ -111,7 +110,11 @@ struct vchiq_mmal_instance;
>  /* normal message context */
>  struct mmal_msg_context {
>  	struct vchiq_mmal_instance *instance;
> -	u32 handle;
> +
> +	/* Index in the context_map idr so that we can find the
> +	 * mmal_msg_context again when servicing the VCHI reply.
> +	 */
> +	int handle;
>  
>  	union {
>  		struct {
> @@ -149,13 +152,6 @@ struct mmal_msg_context {
>  
>  };
>  
> -struct vchiq_mmal_context_map {
> -	/* ensure serialized access to the btree(contention should be low) */
> -	struct mutex lock;
> -	struct btree_head32 btree_head;
> -	u32 last_handle;
> -};
> -
>  struct vchiq_mmal_instance {
>  	VCHI_SERVICE_HANDLE_T handle;
>  
> @@ -165,92 +161,19 @@ struct vchiq_mmal_instance {
>  	/* vmalloc page to receive scratch bulk xfers into */
>  	void *bulk_scratch;
>  
> -	/* mapping table between context handles and mmal_msg_contexts */
> -	struct vchiq_mmal_context_map context_map;
> +	struct idr context_map;
> +	spinlock_t context_map_lock;
>  
>  	/* component to use next */
>  	int component_idx;
>  	struct vchiq_mmal_component component[VCHIQ_MMAL_MAX_COMPONENTS];
>  };
>  
> -static int __must_check
> -mmal_context_map_init(struct vchiq_mmal_context_map *context_map)
> -{
> -	mutex_init(&context_map->lock);
> -	context_map->last_handle = 0;
> -	return btree_init32(&context_map->btree_head);
> -}
> -
> -static void mmal_context_map_destroy(struct vchiq_mmal_context_map *context_map)
> -{
> -	mutex_lock(&context_map->lock);
> -	btree_destroy32(&context_map->btree_head);
> -	mutex_unlock(&context_map->lock);
> -}
> -
> -static u32
> -mmal_context_map_create_handle(struct vchiq_mmal_context_map *context_map,
> -			       struct mmal_msg_context *msg_context,
> -			       gfp_t gfp)
> -{
> -	u32 handle;
> -
> -	mutex_lock(&context_map->lock);
> -
> -	while (1) {
> -		/* just use a simple count for handles, but do not use 0 */
> -		context_map->last_handle++;
> -		if (!context_map->last_handle)
> -			context_map->last_handle++;
> -
> -		handle = context_map->last_handle;
> -
> -		/* check if the handle is already in use */
> -		if (!btree_lookup32(&context_map->btree_head, handle))
> -			break;
> -	}
> -
> -	if (btree_insert32(&context_map->btree_head, handle,
> -			   msg_context, gfp)) {
> -		/* probably out of memory */
> -		mutex_unlock(&context_map->lock);
> -		return 0;
> -	}
> -
> -	mutex_unlock(&context_map->lock);
> -	return handle;
> -}
> -
> -static struct mmal_msg_context *
> -mmal_context_map_lookup_handle(struct vchiq_mmal_context_map *context_map,
> -			       u32 handle)
> -{
> -	struct mmal_msg_context *msg_context;
> -
> -	if (!handle)
> -		return NULL;
> -
> -	mutex_lock(&context_map->lock);
> -
> -	msg_context = btree_lookup32(&context_map->btree_head, handle);
> -
> -	mutex_unlock(&context_map->lock);
> -	return msg_context;
> -}
> -
> -static void
> -mmal_context_map_destroy_handle(struct vchiq_mmal_context_map *context_map,
> -				u32 handle)
> -{
> -	mutex_lock(&context_map->lock);
> -	btree_remove32(&context_map->btree_head, handle);
> -	mutex_unlock(&context_map->lock);
> -}
> -
>  static struct mmal_msg_context *
>  get_msg_context(struct vchiq_mmal_instance *instance)
>  {
>  	struct mmal_msg_context *msg_context;
> +	int handle;
>  
>  	/* todo: should this be allocated from a pool to avoid kzalloc */
>  	msg_context = kzalloc(sizeof(*msg_context), GFP_KERNEL);
> @@ -258,32 +181,40 @@ get_msg_context(struct vchiq_mmal_instance *instance)
>  	if (!msg_context)
>  		return ERR_PTR(-ENOMEM);
>  
> -	msg_context->instance = instance;
> -	msg_context->handle =
> -		mmal_context_map_create_handle(&instance->context_map,
> -					       msg_context,
> -					       GFP_KERNEL);
> +	/* Create an ID that will be passed along with our message so
> +	 * that when we service the VCHI reply, we can look up what
> +	 * message is being replied to.
> +	 */
> +	spin_lock(&instance->context_map_lock);
> +	handle = idr_alloc(&instance->context_map, msg_context,
> +			   0, 0, GFP_KERNEL);
> +	spin_unlock(&instance->context_map_lock);
>  
> -	if (!msg_context->handle) {
> +	if (msg_context->handle < 0) {

handle < 0 ?

>  		kfree(msg_context);
> -		return ERR_PTR(-ENOMEM);
> +		return ERR_PTR(handle);
>  	}
>  
> +	msg_context->instance = instance;
> +	msg_context->handle = handle;
> +
>  	return msg_context;
>  }
>  

Regards
Stefan