From: Oliver Neukum <oneukum@suse.com>
To: David Laight <David.Laight@ACULAB.COM>,
"gregKH@linuxfoundation.org" <gregKH@linuxfoundation.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: UAS: fix alignment of scatter/gather segments
Date: Mon, 29 Apr 2019 15:38:19 +0200 [thread overview]
Message-ID: <1556545099.20085.14.camel@suse.com> (raw)
On Mo, 2019-04-29 at 13:31 +0000, David Laight wrote:
> From: Oliver Neukum
> >
> > + * USB has unusual scatter-gather requirements: the length of each
> > + * scatterlist element except the last must be divisible by the
> > + * Bulk maxpacket value. Fortunately this value is always a
> > + * power of 2. Inform the block layer about this requirement.
> > + */
>
> That isn't the correct restriction for XHCI.
> It has its own perverse restrictions.
> I think they are all handled within the xhci driver.
Yes, but that does not matter. You just cannot assume that only
XHCI will be used with UAS. In particular virtual drivers will
be used.
Regards
Oliver
WARNING: multiple messages have this Message-ID (diff)
From: Oliver Neukum <oneukum@suse.com>
To: David Laight <David.Laight@ACULAB.COM>,
"gregKH@linuxfoundation.org" <gregKH@linuxfoundation.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: Re: [PATCH] UAS: fix alignment of scatter/gather segments
Date: Mon, 29 Apr 2019 15:38:19 +0200 [thread overview]
Message-ID: <1556545099.20085.14.camel@suse.com> (raw)
Message-ID: <20190429133819.D9lsLWMfXX5ALEHwBloeEODiJ1ewQCsjXz4STjYovXM@z> (raw)
In-Reply-To: <f378babbf2f349e59d98a5ab99958d78@AcuMS.aculab.com>
On Mo, 2019-04-29 at 13:31 +0000, David Laight wrote:
> From: Oliver Neukum
> >
> > + * USB has unusual scatter-gather requirements: the length of each
> > + * scatterlist element except the last must be divisible by the
> > + * Bulk maxpacket value. Fortunately this value is always a
> > + * power of 2. Inform the block layer about this requirement.
> > + */
>
> That isn't the correct restriction for XHCI.
> It has its own perverse restrictions.
> I think they are all handled within the xhci driver.
Yes, but that does not matter. You just cannot assume that only
XHCI will be used with UAS. In particular virtual drivers will
be used.
Regards
Oliver
next reply other threads:[~2019-04-29 13:38 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-29 13:38 Oliver Neukum [this message]
2019-04-29 13:38 ` [PATCH] UAS: fix alignment of scatter/gather segments Oliver Neukum
-- strict thread matches above, loose matches on Subject: below --
2019-04-30 14:39 Alan Stern
2019-04-30 14:39 ` [PATCH] " Alan Stern
2019-04-30 9:16 David Laight
2019-04-30 9:16 ` [PATCH] " David Laight
2019-04-29 19:42 Alan Stern
2019-04-29 19:42 ` [PATCH] " Alan Stern
2019-04-29 18:42 Oliver Neukum
2019-04-29 18:42 ` [PATCH] " Oliver Neukum
2019-04-29 17:55 Alan Stern
2019-04-29 17:55 ` [PATCH] " Alan Stern
2019-04-29 16:58 Oliver Neukum
2019-04-29 16:58 ` [PATCH] " Oliver Neukum
2019-04-29 16:08 Alan Stern
2019-04-29 16:08 ` [PATCH] " Alan Stern
2019-04-29 15:57 Oliver Neukum
2019-04-29 15:57 ` [PATCH] " Oliver Neukum
2019-04-29 15:06 David Laight
2019-04-29 15:06 ` [PATCH] " David Laight
2019-04-29 14:32 Oliver Neukum
2019-04-29 14:32 ` [PATCH] " Oliver Neukum
2019-04-29 14:19 David Laight
2019-04-29 14:19 ` [PATCH] " David Laight
2019-04-29 13:31 David Laight
2019-04-29 13:31 ` [PATCH] " David Laight
2019-04-29 12:20 Oliver Neukum
2019-04-29 12:20 ` [PATCH] " Oliver Neukum
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