From 71723a96b8b1367fefc18f60025dae792477d602 Mon Sep 17 00:00:00 2001 From: Geert Uytterhoeven Date: Fri, 17 Jan 2020 16:30:56 +0100 Subject: dmaengine: Create symlinks between DMA channels and slaves MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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:" 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 Tested-by: Niklas Söderlund Link: https://lore.kernel.org/r/20200117153056.31363-1-geert+renesas@glider.be Signed-off-by: Vinod Koul --- drivers/dma/dmaengine.c | 37 +++++++++++++++++++++++++++++++------ 1 file changed, 31 insertions(+), 6 deletions(-) (limited to 'drivers/dma') 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); -- cgit v1.2.3