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SubjectRe: [PATCH] staging: bcm2835-camera: Replace open-coded idr with a struct idr.
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Stefan Wahren <stefan.wahren@i2se.com> writes:

> Hi Eric,
>
>> Eric Anholt <eric@anholt.net> 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@anholt.net>
>> ---
>> .../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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