On Wed, Jul 27, 2016 at 02:32:58PM -0700, Viresh Kumar wrote:
The DMA device can't be registered if it doesn't have any channels registered at all. Moreover, it leads to memory leak and is reported by kmemleak as (on 3.10 kernel, and same shall happen on mainline):
unreferenced object 0xffffffc09e597240 (size 64): comm "swapper/0", pid 1, jiffies 4294877736 (age 7060.280s) hex dump (first 32 bytes): 00 00 00 00 c0 ff ff ff 30 00 00 ff 00 00 00 ff ........0....... 00 00 00 ff 00 00 00 ff 00 00 00 ff 00 00 00 ff ................ backtrace: [<ffffffc0003079ec>] create_object+0x148/0x2a0 [<ffffffc000cc150c>] kmemleak_alloc+0x80/0xbc [<ffffffc000303a7c>] kmem_cache_alloc_trace+0x120/0x1ac [<ffffffc00054771c>] dma_async_device_register+0x160/0x46c [<ffffffc000548958>] foo_probe+0x1a0/0x264 [<ffffffc0005d6658>] platform_drv_probe+0x14/0x20 [<ffffffc0005d50cc>] driver_probe_device+0x160/0x374 [<ffffffc0005d538c>] __driver_attach+0x60/0x90 [<ffffffc0005d3e78>] bus_for_each_dev+0x7c/0xb0 [<ffffffc0005d4a0c>] driver_attach+0x1c/0x28 [<ffffffc0005d459c>] bus_add_driver+0x124/0x248 [<ffffffc0005d59cc>] driver_register+0x90/0x110 [<ffffffc0005d6bf4>] platform_driver_register+0x58/0x64 [<ffffffc00142a70c>] foo_driver_init+0x10/0x1c [<ffffffc000200878>] do_one_initcall+0xac/0x148 [<ffffffc00140096c>] kernel_init_freeable+0x1a0/0x258
Return -ENODEV from dma_async_device_register() on such a case.
Signed-off-by: Viresh Kumar viresh.kumar@linaro.org
Hi Vinod,
Sorry if the fundamentals behind this patch are completely incorrect, i.e. We *can't* register a dma device with 0 channels. Its been long that I have worked on dma stuff :)
This sounds okay, but why would anyone register a device without having a channel?
drivers/dma/dmaengine.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index 8c9f45fd55fc..6b535262ac5d 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -997,6 +997,13 @@ int dma_async_device_register(struct dma_device *device) } chan->client_count = 0; }
- if (!chancnt) {
dev_err(device->dev, "%s: device has no channels!\n", __func__);rc = -ENODEV;goto err_out;- }
- device->chancnt = chancnt;
mutex_lock(&dma_list_mutex); -- 2.7.4