On Mon, May 05, 2025 at 10:11:23AM +0200, Christoph Hellwig wrote:
> usb-storage is the last user of the block layer bounce buffering now,
> and only uses it for HCDs that do not support DMA on highmem configs.
>
> Remove this support and fail the probe so that the block layer bounce
> buffering can go away.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
Reviewed-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/usb/storage/usb.c | 20 ++++++++++++++------
> 1 file changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
> index d36f3b6992bb..152ee3376550 100644
> --- a/drivers/usb/storage/usb.c
> +++ b/drivers/usb/storage/usb.c
> @@ -1056,13 +1056,20 @@ int usb_stor_probe1(struct us_data **pus,
> goto BadDevice;
>
> /*
> - * Some USB host controllers can't do DMA; they have to use PIO.
> - * For such controllers we need to make sure the block layer sets
> - * up bounce buffers in addressable memory.
> + * Some USB host controllers can't do DMA: They have to use PIO, or they
> + * have to use a small dedicated local memory area, or they have other
> + * restrictions on addressable memory.
> + *
> + * We can't support these controllers on highmem systems as we don't
> + * kmap or bounce buffer.
> */
> - if (!hcd_uses_dma(bus_to_hcd(us->pusb_dev->bus)) ||
> - bus_to_hcd(us->pusb_dev->bus)->localmem_pool)
> - host->no_highmem = true;
> + if (IS_ENABLED(CONFIG_HIGHMEM) &&
> + (!hcd_uses_dma(bus_to_hcd(us->pusb_dev->bus)) ||
> + bus_to_hcd(us->pusb_dev->bus)->localmem_pool)) {
> + dev_warn(&intf->dev, "USB Mass Storage not supported on this host controller\n");
> + result = -EINVAL;
> + goto release;
> + }
>
> /* Get the unusual_devs entries and the descriptors */
> result = get_device_info(us, id, unusual_dev);
> @@ -1081,6 +1088,7 @@ int usb_stor_probe1(struct us_data **pus,
>
> BadDevice:
> usb_stor_dbg(us, "storage_probe() failed\n");
> +release:
> release_everything(us);
> return result;
> }
