From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:6f8:1178:4:290:27ff:fe1d:cc33]) by canuck.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1Qodjw-0003jK-0U for barebox@lists.infradead.org; Wed, 03 Aug 2011 15:52:13 +0000 Date: Wed, 3 Aug 2011 17:52:08 +0200 From: Sascha Hauer Message-ID: <20110803155208.GT31404@pengutronix.de> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: barebox-bounces@lists.infradead.org Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: problem in serial_ns16550.c To: Antony Pavlov Cc: barebox 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. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox