diff options
| author | Christoph Hellwig <hch@lst.de> | 2020-09-10 18:03:49 +0200 |
|---|---|---|
| committer | Christoph Hellwig <hch@lst.de> | 2020-09-17 18:43:25 +0200 |
| commit | 6eb0233ec2d0df288fe8515d5b0b2b15562e05bb (patch) | |
| tree | c1783ef708221981298dc653bbaa7db2c851e1cb /drivers/usb/core/usb.c | |
| parent | cf141ae989e2ff119cd320326da5923b480d1641 (diff) | |
usb: don't inherity DMA properties for USB devices
As the comment in usb_alloc_dev correctly states, drivers can't use
the DMA API on usb device, and at least calling dma_set_mask on them
is highly dangerous. Unlike what the comment states upper level drivers
also can't really use the presence of a dma mask to check for DMA
support, as the dma_mask is set by default for most busses.
Setting the dma_mask comes from "[PATCH] usbcore dma updates (and doc)"
in BitKeeper times, as it seems like it was primarily for setting the
NETIF_F_HIGHDMA flag in USB drivers, something that has long been
fixed up since.
Setting the dma_pfn_offset comes from commit b44bbc46a8bb
("usb: core: setup dma_pfn_offset for USB devices and, interfaces"),
which worked around the fact that the scsi_calculate_bounce_limits
functions wasn't going through the proper driver interface to query
DMA information, but that function was removed in commit 21e07dba9fb1
("scsi: reduce use of block bounce buffers") years ago.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/core/usb.c')
| -rw-r--r-- | drivers/usb/core/usb.c | 12 |
1 files changed, 0 insertions, 12 deletions
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c index bafc113f2b3e..9b4ac4415f1a 100644 --- a/drivers/usb/core/usb.c +++ b/drivers/usb/core/usb.c @@ -599,18 +599,6 @@ struct usb_device *usb_alloc_dev(struct usb_device *parent, dev->dev.bus = &usb_bus_type; dev->dev.type = &usb_device_type; dev->dev.groups = usb_device_groups; - /* - * Fake a dma_mask/offset for the USB device: - * We cannot really use the dma-mapping API (dma_alloc_* and - * dma_map_*) for USB devices but instead need to use - * usb_alloc_coherent and pass data in 'urb's, but some subsystems - * manually look into the mask/offset pair to determine whether - * they need bounce buffers. - * Note: calling dma_set_mask() on a USB device would set the - * mask for the entire HCD, so don't do that. - */ - dev->dev.dma_mask = bus->sysdev->dma_mask; - dev->dev.dma_pfn_offset = bus->sysdev->dma_pfn_offset; set_dev_node(&dev->dev, dev_to_node(bus->sysdev)); dev->state = USB_STATE_ATTACHED; dev->lpm_disable_count = 1; |