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Date: Thu, 11 Apr 2019 13:05:20 +0000 From: "Adamski, Krzysztof (Nokia - PL/Wroclaw)" <krzysztof.adamski@...ia.com> To: "Enrico Weigelt, metux IT consult" <lkml@...ux.net> CC: Vincent Whitchurch <vincent.whitchurch@...s.com>, Greg KH <gregkh@...uxfoundation.org>, "jslaby@...e.com" <jslaby@...e.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] tty: Add NULL TTY driver On Fri, Apr 05, 2019 at 02:32:41PM +0200, Enrico Weigelt, metux IT consult wrote: >On 05.04.19 11:00, Vincent Whitchurch wrote: >> On Fri, Apr 05, 2019 at 10:39:43AM +0200, Enrico Weigelt, metux IT consult wrote: >>> On 03.04.19 16:11, Vincent Whitchurch wrote: >>> >>>> Especially on embedded systems, it would be convenient to have a simple >>>> way to disable the console (both for kernel and userspace) on a system >>>> which normally uses it, to free up the UART for other things. >>> >>> Just symlinking to /dev/null does not work ? >> >> No, /dev/null does not support the TTY ioctls. > >hmm, wo (which programs) do you need, that really need them ? > >>> OTOH, if you're introducing a dummy console, wouldn't a ringbuffer that, >>> can be read out later, a better option ? >> >> There is already a ttyprintk driver in mainline to send these messages >> to the printk ring buffer if one is actually intrested in what is >> written to the console. There's no option to enable it via console= in >> mainline but I have a patch for that too. > >Great. IMHO, that would be the better way. There are (embedded) cases where the kernel ring buffer is stored for log inspection and all the logs that are *not* wanted there (like interactive debug logs, some progress bar, etc) are send specifically to /dev/console to avoid sending them to normal log store (as they are only useful when debugging over console). In non-debug mode /dev/console becomes /dev/null to speed things up. I would personally benefit from Vincents patch. In fact I found this thread because I was considering doing exactly the same for our system. Krzysztof
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