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Date: Thu, 17 Jan 2013 10:55:45 +0000 From: Will Deacon <will.deacon@....com> To: Pratik Patel <pratikp@...eaurora.org> Cc: Jon Hunter <jon-hunter@...com>, "linux@....linux.org.uk" <linux@....linux.org.uk>, "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>, "linus.walleij@...aro.org" <linus.walleij@...aro.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "magnus.p.persson@...ricsson.com" <magnus.p.persson@...ricsson.com>, "david.rusling@...aro.org" <david.rusling@...aro.org>, "arve@...roid.com" <arve@...roid.com>, "dsaxena@...aro.org" <dsaxena@...aro.org>, "john.stultz@...aro.org" <john.stultz@...aro.org>, "d-deao@...com" <d-deao@...com>, "christian.bejram@...ricsson.com" <christian.bejram@...ricsson.com>, "devicetree-discuss@...ts.ozlabs.org" <devicetree-discuss@...ts.ozlabs.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org> Subject: Re: CoreSight framework and drivers On Wed, Jan 16, 2013 at 12:14:59AM +0000, Pratik Patel wrote: > On Mon, Jan 07, 2013 at 11:58:36AM +0000, Will Deacon wrote: > > On Thu, Jan 03, 2013 at 06:06:43PM +0000, Pratik Patel wrote: > > > Whats the advantage in using debugfs here? > > > > The main things I like about debugfs are (a) it's a text-driven interface > > and easy to script with and (b) it matches what we do for ftrace. > > > > Furthermore, it means that subtle differences between devices can be hidden > > in the driver and not require different vendor tools for parsing the trace > > data. > > > Sorry for the delay and maybe I am missing something but it seems > we can take care of such protocol or parsing/decoding differences > even with device nodes since that seems independent of the > interface used - per device debugfs attributes or per device > device nodes. You seem to be arguing that the two interfaces are equivalent, in which case I say that we should follow ftrace's lead and use debugfs for this... ...but I still maintain that debugfs is also far easier to work with from userspace. > CoreSight trace solution is typically a SoC wide solution and > hence can get used by non-Linux processors or hardware. Using > debugfs would imply compiling it and exposing all the debug > knobs even if the use case was to use the CoreSight solution for > something that didn't need all that. Many debug features require debugfs to be compiled, so I don't buy that as a show-stopping argument in favour of using dev nodes. I also think that exposing all of the debug knobs is actually a good thing, given the low-level nature of coresight devices (where we're offloading most of the knowledge to userspace anyway). Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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