summaryrefslogtreecommitdiffstats
path: root/drivers/dma
diff options
context:
space:
mode:
authorGeert Uytterhoeven <geert+renesas@glider.be>2020-01-17 16:30:56 +0100
committerVinod Koul <vkoul@kernel.org>2020-01-24 11:41:32 +0530
commit71723a96b8b1367fefc18f60025dae792477d602 (patch)
tree3b1f3f47cfa643fbbcac9d3c15fbac210f808382 /drivers/dma
parente9f08b65250d73ab70e79e194813f52b8d306784 (diff)
downloadlinux-stable-71723a96b8b1367fefc18f60025dae792477d602.tar.gz
linux-stable-71723a96b8b1367fefc18f60025dae792477d602.tar.bz2
linux-stable-71723a96b8b1367fefc18f60025dae792477d602.zip
dmaengine: Create symlinks between DMA channels and slaves
Currently it is not easy to find out which DMA channels are in use, and which slave devices are using which channels. Fix this by creating two symlinks between the DMA channel and the actual slave device when a channel is requested: 1. A "slave" symlink from DMA channel to slave device, 2. A "dma:<name>" symlink slave device to DMA channel. When the channel is released, the symlinks are removed again. The latter requires keeping track of the slave device and the channel name in the dma_chan structure. Note that this is limited to channel request functions for requesting an exclusive slave channel that take a device pointer (dma_request_chan() and dma_request_slave_channel*()). Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Tested-by: Niklas Söderlund <niklas.soderlund@ragnatech.se> Link: https://lore.kernel.org/r/20200117153056.31363-1-geert+renesas@glider.be Signed-off-by: Vinod Koul <vkoul@kernel.org>
Diffstat (limited to 'drivers/dma')
-rw-r--r--drivers/dma/dmaengine.c37
1 files changed, 31 insertions, 6 deletions
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 51a2f2b1b2de..f3ef4edd4de1 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -60,6 +60,8 @@ static long dmaengine_ref_count;
/* --- sysfs implementation --- */
+#define DMA_SLAVE_NAME "slave"
+
/**
* dev_to_dma_chan - convert a device pointer to its sysfs container object
* @dev - device node
@@ -730,11 +732,11 @@ struct dma_chan *dma_request_chan(struct device *dev, const char *name)
if (has_acpi_companion(dev) && !chan)
chan = acpi_dma_request_slave_chan_by_name(dev, name);
- if (chan) {
- /* Valid channel found or requester needs to be deferred */
- if (!IS_ERR(chan) || PTR_ERR(chan) == -EPROBE_DEFER)
- return chan;
- }
+ if (PTR_ERR(chan) == -EPROBE_DEFER)
+ return chan;
+
+ if (!IS_ERR_OR_NULL(chan))
+ goto found;
/* Try to find the channel via the DMA filter map(s) */
mutex_lock(&dma_list_mutex);
@@ -754,7 +756,23 @@ struct dma_chan *dma_request_chan(struct device *dev, const char *name)
}
mutex_unlock(&dma_list_mutex);
- return chan ? chan : ERR_PTR(-EPROBE_DEFER);
+ if (!IS_ERR_OR_NULL(chan))
+ goto found;
+
+ return ERR_PTR(-EPROBE_DEFER);
+
+found:
+ chan->slave = dev;
+ chan->name = kasprintf(GFP_KERNEL, "dma:%s", name);
+ if (!chan->name)
+ return ERR_PTR(-ENOMEM);
+
+ if (sysfs_create_link(&chan->dev->device.kobj, &dev->kobj,
+ DMA_SLAVE_NAME))
+ dev_err(dev, "Cannot create DMA %s symlink\n", DMA_SLAVE_NAME);
+ if (sysfs_create_link(&dev->kobj, &chan->dev->device.kobj, chan->name))
+ dev_err(dev, "Cannot create DMA %s symlink\n", chan->name);
+ return chan;
}
EXPORT_SYMBOL_GPL(dma_request_chan);
@@ -812,6 +830,13 @@ void dma_release_channel(struct dma_chan *chan)
/* drop PRIVATE cap enabled by __dma_request_channel() */
if (--chan->device->privatecnt == 0)
dma_cap_clear(DMA_PRIVATE, chan->device->cap_mask);
+ if (chan->slave) {
+ sysfs_remove_link(&chan->slave->kobj, chan->name);
+ kfree(chan->name);
+ chan->name = NULL;
+ chan->slave = NULL;
+ }
+ sysfs_remove_link(&chan->dev->device.kobj, DMA_SLAVE_NAME);
mutex_unlock(&dma_list_mutex);
}
EXPORT_SYMBOL_GPL(dma_release_channel);