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

[Eric Anholt]

Stefan Wahren <stefan.wahren@xxxxxxxx> writes:

> 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 ?

You're right, thanks!

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