From mboxrd@z Thu Jan 1 00:00:00 1970 From: chri Subject: Re: [PATCH] max3100 driver Date: Sat, 20 Sep 2008 12:35:26 +0200 Message-ID: References: <1221895208650-git-send-email-chripell@gmail.com> <20080920012454.e40f03cc.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from rv-out-0506.google.com ([209.85.198.225]:20561 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751316AbYITKf1 (ORCPT ); Sat, 20 Sep 2008 06:35:27 -0400 Received: by rv-out-0506.google.com with SMTP id k40so815380rvb.1 for ; Sat, 20 Sep 2008 03:35:26 -0700 (PDT) In-Reply-To: <20080920012454.e40f03cc.akpm@linux-foundation.org> Content-Disposition: inline Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org Sorry, sent HTML mail by mistake, so resending :-/ On Sat, Sep 20, 2008 at 10:24 AM, Andrew Morton wrote: > > +#define MAX3100_MAJOR 204 > > Allocating a new major is a Big Deal. It involves getting the major > registered by contacting device@lanana.org. > > It's better to dynamically allocate it - let udev handle it. > I looked at other serial driver as an example and checked devices.txt: if I don't get it wrong major 204 should be already reserved for serial port. Anyway I choose a minor number already allocated by mistake (did not see the "...") and will correct that. Is this ok or I *have to* move to dynamic major (it's a bit a nuisance since max3100 is used in embedded system where udev is not always used)? > `struct max3100_port' is sufficient, and would be more typical. > > > + struct uart_port port; > > + struct spi_device *spi; > > + > > + int cts:1; /* last CTS received for flow ctrl */ > > + int tx_empty:1; /* last TX empty bit */ > > These two bits will share a word and hence locking is needed to prevent > modifications to one from trashing modifications to the other on SMP. > > That's OK, but it would be best to document that locking right here, and > to check that it is adhered to. > I did not realize this until you explained me. I'm not sure if actual packing of bit-fields is implementation dependent but I think so. If this is right I guess it's better to avoid bit-fields in structs that can be accessed concurrently (or otherwise I have to lock the entire struct). So, should I avoid bit-fields altogether? I will correct the patch and resend. Thanks, -- Christian Pellegrin, see http://www.evolware.org/chri/ "Real Programmers don't play tennis, or any other sport which requires you to change clothes. Mountain climbing is OK, and Real Programmers wear their climbing boots to work in case a mountain should suddenly spring up in the middle of the computer room."