From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Subject: Re: [PATCH v3 1/1] serial: imx - Add dma buffer confugration via sysfs Date: Fri, 9 Nov 2018 09:02:57 -0800 Message-ID: <20181109170257.GA14151@kroah.com> References: <1539249903-6316-1-git-send-email-fabien.lahoudere@collabora.com> <20181015140118.GA16234@kroah.com> <1539764425.3694.1.camel@collabora.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <1539764425.3694.1.camel@collabora.com> Sender: linux-kernel-owner@vger.kernel.org To: Fabien Lahoudere Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org List-Id: linux-serial@vger.kernel.org On Wed, Oct 17, 2018 at 10:20:25AM +0200, Fabien Lahoudere wrote: > Hi Greg, > > On Mon, 2018-10-15 at 16:01 +0200, Greg KH wrote: > > On Thu, Oct 11, 2018 at 11:25:03AM +0200, Fabien Lahoudere wrote: > > > In order to optimize serial communication on imx53 and imx6, we may > > > need to tweak DMA period and buffer length per period. > > > > Why can you not just automatically determine this information?  What is > > userspace going to know that the kernel can not just learn now? > > > > Having tunables is nice, but it is even better to not need them at all. > > I agree that it is better to let the kernel do the configuration. Great! > However in our case we use several serial communication for different device > and one of them need to tweak that configuration to get small data with a better > period. However having this parameter for all serial port implies a bigger number > of interrupts for others too. Why can you not dynamically figure this out? How are you figuring it out "by hand" today in userspace? thanks, greg k-h