From 7cc5bf9a3a84e5a02e23e5739fb894790b37c101 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Tue, 8 Jul 2008 11:58:21 -0700 Subject: dmaengine: track the number of clients using a channel Haavard's dma-slave interface would like to test for exclusive access to a channel. The standard channel refcounting is not sufficient in that it tracks more than just client references, it is also inaccurate as reference counts are percpu until the channel is removed. This change also enables a future fix to deallocate resources when a client declines to use a capable channel. Acked-by: Haavard Skinnemoen Signed-off-by: Dan Williams --- drivers/dma/dmaengine.c | 14 ++++++++++---- include/linux/dmaengine.h | 2 ++ 2 files changed, 12 insertions(+), 4 deletions(-) diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index 99c22b42bada..10de69eb1a3e 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -183,9 +183,10 @@ static void dma_client_chan_alloc(struct dma_client *client) /* we are done once this client rejects * an available resource */ - if (ack == DMA_ACK) + if (ack == DMA_ACK) { dma_chan_get(chan); - else if (ack == DMA_NAK) + chan->client_count++; + } else if (ack == DMA_NAK) return; } } @@ -272,8 +273,10 @@ static void dma_clients_notify_removed(struct dma_chan *chan) /* client was holding resources for this channel so * free it */ - if (ack == DMA_ACK) + if (ack == DMA_ACK) { dma_chan_put(chan); + chan->client_count--; + } } mutex_unlock(&dma_list_mutex); @@ -313,8 +316,10 @@ void dma_async_client_unregister(struct dma_client *client) ack = client->event_callback(client, chan, DMA_RESOURCE_REMOVED); - if (ack == DMA_ACK) + if (ack == DMA_ACK) { dma_chan_put(chan); + chan->client_count--; + } } list_del(&client->global_node); @@ -394,6 +399,7 @@ int dma_async_device_register(struct dma_device *device) kref_get(&device->refcount); kref_get(&device->refcount); kref_init(&chan->refcount); + chan->client_count = 0; chan->slow_ref = 0; INIT_RCU_HEAD(&chan->rcu); } diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index d08a5c5eb928..6432b8343220 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -139,6 +139,7 @@ struct dma_chan_percpu { * @rcu: the DMA channel's RCU head * @device_node: used to add this to the device chan list * @local: per-cpu pointer to a struct dma_chan_percpu + * @client-count: how many clients are using this channel */ struct dma_chan { struct dma_device *device; @@ -154,6 +155,7 @@ struct dma_chan { struct list_head device_node; struct dma_chan_percpu *local; + int client_count; }; #define to_dma_chan(p) container_of(p, struct dma_chan, dev) -- cgit v1.2.3