From: Christoph Hellwig <hch@lst.de>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Christoph Hellwig <hch@lst.de>,
linux-usb@vger.kernel.org, usb-storage@lists.one-eyed-alien.net,
linux-scsi@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: usb-storage: stop using block layer bounce buffers
Date: Fri, 27 Apr 2018 07:27:31 +0200 [thread overview]
Message-ID: <20180427052731.GA9799@lst.de> (raw)
On Sun, Apr 15, 2018 at 11:24:11AM -0400, Alan Stern wrote:
> On Sun, 15 Apr 2018, Christoph Hellwig wrote:
>
> > USB host controllers now must handle highmem, so we can get rid of bounce
> > buffering highmem pages in the block layer.
>
> Sorry, I don't quite understand what you are saying. Do you mean that
> all USB host controllers now magically _do_ handle highmem? Or do you
> mean that if they _don't_ handle highmem, we will not support them any
> more?
USB controller themselves never cared about highmem, drivers did. For
PIO based controllers they'd have to kmap any address no in the kernel
drirect mapping.
Nothing in drivers/usb/host or the other diretories related to host
drivers calls page_address (only used in a single gadget) or sg_virt
(only used in a few upper level drivers), which makes me assume
semi-confidently that no USB host driver is not highmem aware these
days.
Greg, does this match your observation as the USB maintainer?
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next reply other threads:[~2018-04-27 5:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-27 5:27 Christoph Hellwig [this message]
-- strict thread matches above, loose matches on Subject: below --
2018-05-02 14:48 usb-storage: stop using block layer bounce buffers Alan Stern
2018-05-02 12:47 Christoph Hellwig
2018-04-27 14:09 Alan Stern
2018-04-15 15:24 Alan Stern
2018-04-15 14:53 Christoph Hellwig
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