Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751799AbaK0NpX (ORCPT ); Thu, 27 Nov 2014 08:45:23 -0500 Received: from mail-ie0-f174.google.com ([209.85.223.174]:61550 "EHLO mail-ie0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751768AbaK0NpV (ORCPT ); Thu, 27 Nov 2014 08:45:21 -0500 MIME-Version: 1.0 In-Reply-To: <20141127131635.GJ2361@bivouac.eciton.net> References: <1417023640-23464-1-git-send-email-leif.lindholm@linaro.org> <1417023640-23464-3-git-send-email-leif.lindholm@linaro.org> <20141126183052.GH3443@lunn.ch> <20141126214847.GJ3443@lunn.ch> <20141127121543.GG857@leverpostej> <20141127131635.GJ2361@bivouac.eciton.net> From: Grant Likely Date: Thu, 27 Nov 2014 13:45:00 +0000 X-Google-Sender-Auth: nS4ebmOWk7kh0OFEnTqz6mIykQg Message-ID: Subject: Re: [PATCH v2 2/2] of: support passing console options with stdout-path To: Leif Lindholm Cc: Mark Rutland , Andrew Lunn , "devicetree@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Linux Kernel Mailing List , Rob Herring , Jean-Christophe PLAGNIOL-VILLARD , Ian Campbell , "s.hauer@pengutronix.de" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 27, 2014 at 1:16 PM, Leif Lindholm wrote: > On Thu, Nov 27, 2014 at 12:15:43PM +0000, Mark Rutland wrote: >> On Wed, Nov 26, 2014 at 09:48:47PM +0000, Andrew Lunn wrote: >> > On Wed, Nov 26, 2014 at 09:07:33PM +0000, Grant Likely wrote: >> > > On Wed, Nov 26, 2014 at 6:30 PM, Andrew Lunn wrote: >> > > > On Wed, Nov 26, 2014 at 05:40:40PM +0000, Leif Lindholm wrote: >> > > >> Support specifying console options (like with console=ttyXN,) >> > > >> by appending them to the stdout-path property after a separating ':'. >> > > >> >> > > >> Example: >> > > >> stdout-path = "uart0:115200"; >> > > > >> > > > Hi Leif >> > > > >> > > > This should be documented somewhere under >> > > > Documentation/devicetree/bindings/ >> > > > >> > > > Not sure where thought. Maybe a top level chosen.txt? >> > > >> > > Actually, this one doesn't. It is already documented in ePAPR >> > >> > Hi Grant >> > >> > Humm, do i have an old version of ePAPR? >> > >> > All i see is that in Table 3-4 It says: >> > >> > stdout-path O A string that specifies the full path to the >> > node representing the device to be used for >> > boot console output. If the character ":" is >> > present in the value it terminates the >> > path. The value may be an alias. >> > >> > If the stdin-path property is not specified, >> > stdout-path should be assumed to define the input device. >> > >> > So what is before the : is defined. What comes afterwards, >> > baudrate/parity/bits/flow control does not appear to the defined in >> > ePAPR. Should we not document the extension being added here? >> >> I believe that we should, and it should be relatively trivial to add a >> document stating that the format and meaning of the parts after the ':' >> are device-specific. > > Device-specific is a bit broad though? Not really, but the expectation should be quite strong that for UARTs, the first argument after the ':' is the b/p/b/f string. We could also specify that ',' is used as a separator when multiple arguments are to be passed to a device. > >> So how about Documentation/devicetree/bindings/serial/stdout-path.txt, >> with something like the following: > > There is, however, nothing serial-specific about this functionality - > it console-specific. > > Could it be bindings/console/stdout-path.txt? > >> ---->8---- >> Device trees may specify the device to be used for boot console output >> with a stdout-path property under /chosen, as described in ePAPR, e.g. >> >> / { >> chosen { >> stdout-path = "/serial@f00:115200"; >> }; >> >> serial@f00 { >> compatible = "vendor,some-uart"; >> reg = <0xf00 0x10>; >> }; >> }; >> >> If the character ":" is present in the value, this terminates the path. >> The meaning of any cahracters following the ":" is device-specific, and >> must be specified in the relevant binding documentation. >> ---->8---- >> >> The more difficult part is documenting those (and I'm still uneasy about >> conflating the Linux driver command line options with the DT binding for >> that reason). > > For the current situation, which _is_ serial-specific, could we then > add a serial/stdout-path.txt describing the mapping to > uart_parse_options - making that interface an implicit requirement for > the use of stdout-path? Put it in Documentation/devicetree/bindings/chosen.txt We may as well have one file for all the common stuff that goes into chosen. g. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/