From: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: barebox <barebox@lists.infradead.org>
Subject: Re: problem in serial_ns16550.c
Date: Wed, 3 Aug 2011 18:38:08 +0200 [thread overview]
Message-ID: <20110803163808.GE24730@game.jcrosoft.org> (raw)
In-Reply-To: <20110803155208.GT31404@pengutronix.de>
On 17:52 Wed 03 Aug , Sascha Hauer wrote:
> On Wed, Aug 03, 2011 at 07:35:18PM +0400, Antony Pavlov wrote:
> > Hi!
> >
> > IMHO there is a problem in ns16550_probe() (see
> > drivers/serial/serial_ns16550.c:243).
> >
> > There is the construction:
> > ------
> > if (!(dev->resource[0].flags & IORESOURCE_MEM_TYPE_MASK) &&
> > ((plat->reg_read == NULL) || (plat->reg_write == NULL)))
> > return -EINVAL;
> > ------
> >
> > Imagine creation of typical serial port:
> > ------
> > static struct NS16550_plat plat = {
> > .clock = 1843200,
> > };
> >
> > ...
> >
> > add_ns16550_device(-1, UART_ADDR, 8, IORESOURCE_MEM_8BIT, &plat);
> > ------
> >
> > Here we have plat.reg_read == NULL, plat.reg_write == NULL.
> > Usage of add_ns16550_device will make
> > dev->resource[0].flags & IORESOURCE_MEM_TYPE_MASK == IORESOURCE_MEM_8BIT.
> >
> > But take into account this (see include/linux/ioport.h):
> > ------
> > #define IORESOURCE_MEM_TYPE_MASK (3<<3)
> > #define IORESOURCE_MEM_8BIT (0<<3)
> > ------
> >
> > So IORESOURCE_MEM_8BIT == 0 (sic!)
> >
> > A son tour, !(dev->resource[0].flags & IORESOURCE_MEM_TYPE_MASK) give
> > true, if flags select IORESOURCE_MEM_8BIT.
> >
> > As a result, if add_ns16550_device() take IORESOURCE_MEM_8BIT, and
> > plat->reg_read == NULL, plat->reg_write == NULL then ns16550_probe()
> > will return -EINVAL.
>
> Ok, then we have to check for the existence of plat->reg_read/write
> first. If the exist, we have to skip further IORESOURCE_MEM_xBIT checks.
> If they don't exist we do whatever IORESOURCE_MEM_xBIT indicates.
>
> That only leaves the problem that if a user registers a ns16550 driver
> without reg_read/write and does not care about resource types either
> the driver defaults to 8 bit mmio accesses, but I think we can live with
> that.
that was my idea at the beginning
Best Regards,
J.
_______________________________________________
barebox mailing list
barebox@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/barebox
next prev parent reply other threads:[~2011-08-03 16:56 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-03 15:35 Antony Pavlov
2011-08-03 15:52 ` Sascha Hauer
2011-08-03 16:38 ` Jean-Christophe PLAGNIOL-VILLARD [this message]
2011-08-03 16:35 ` Jean-Christophe PLAGNIOL-VILLARD
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20110803163808.GE24730@game.jcrosoft.org \
--to=plagnioj@jcrosoft.com \
--cc=barebox@lists.infradead.org \
--cc=s.hauer@pengutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox