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[72.189.64.225]) by smtp.gmail.com with ESMTPSA id q68sm17443130qke.123.2020.08.02.14.11.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 02 Aug 2020 14:11:44 -0700 (PDT) Date: Sun, 2 Aug 2020 17:11:42 -0400 From: William Breathitt Gray To: David Lechner Subject: Re: [PATCH v4 3/5] counter: Add character device interface Message-ID: <20200802211142.GB606173@shinobu> References: <08b3ac7349a59ba7fa5cd438bbe78360842ccd11.1595358237.git.vilhelm.gray@gmail.com> <415ee9ad-255e-cee7-22a6-ffa977999691@lechnology.com> MIME-Version: 1.0 In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200802_171146_820395_D0E3CEEA X-CRM114-Status: GOOD ( 26.81 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kamel.bouhara@bootlin.com, gwendal@chromium.org, alexandre.torgue@st.com, linux-iio@vger.kernel.org, patrick.havelange@essensium.com, alexandre.belloni@bootlin.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, mcoquelin.stm32@gmail.com, fabrice.gasnier@st.com, syednwaris@gmail.com, linux-stm32@st-md-mailman.stormreply.com, jic23@kernel.org Content-Type: multipart/mixed; boundary="===============8807342266481237102==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============8807342266481237102== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="NDin8bjvE/0mNLFQ" Content-Disposition: inline --NDin8bjvE/0mNLFQ Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Jul 30, 2020 at 05:49:37PM -0500, David Lechner wrote: > On 7/28/20 7:20 PM, David Lechner wrote: > > On 7/21/20 2:35 PM, William Breathitt Gray wrote: > >> This patch introduces a character device interface for the Counter > >> subsystem. Device data is exposed through standard character device re= ad > >> operations. Device data is gathered when a Counter event is pushed by > >> the respective Counter device driver. Configuration is handled via ioc= tl > >> operations on the respective Counter character device node. > >=20 > > This sounds similar to triggers and buffers in the iio subsystem. And > > I can see how it might be useful in some cases. But I think it would not > > give the desired results when performance is important. > >=20 >=20 > By the way, I really appreciate the work you have done here. When reviewi= ng > code, it is easy to point out what is wrong or we don't like and to not > mention all the parts that are good. And there is a lot of really good wo= rk > here already. >=20 > I've been working on this all week to try out some of my suggestions and > I'm not getting very far. This is a very difficult problem to solve! >=20 > I just wanted to mention this since I responded to this patch series > already but I am still learning and trying things. So I may have more/ > different feedback in the future and I may decide some of my suggestions > are not so good. :-) >=20 > And one more thing, there was a nice talk at the Embedded Linux > Conference last month about lessons learned from designing a userspace > API for the GPIO subsystem [1]. Unfortunately, there is no video yet, > but the slides might have some helpful ideas about mistakes to avoid. >=20 > [1]: https://elinux.org/ELC_2020_Presentations Thanks! I appreciate the words of encouragement. :-) This is a big endeavor so I'm expecting a lot of mistakes and changes along the way. Since we're designing a new userspace interface as well, I want to make sure it's correct before we commit it, because when it's finally introduced we're basically stuck with it. So I'm happy when mistakes are found because it saves me from having to live with those later after the interface is live. I'll respond to your PATCH 3/5 review later this week or coming weekend when I get the chance. Thanks again, William Breathitt Gray --NDin8bjvE/0mNLFQ Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEk5I4PDJ2w1cDf/bghvpINdm7VJIFAl8nLA0ACgkQhvpINdm7 VJInMhAAqVGmbjhms6aBJfCZ+LH6WB9U1RvePeF1nw9cH70V1Wiw0/OLYGMYm1YX zuhQrO8cc20cSWVQgrdl2m6ykbhShMGK1BzJiMW+ehYVdUZWOygKrNJRxxzGyo2m DLHJox16JauHPhwZhxCx+ZDmzDbC0P99H16CsGYccxlFkbGb4MZgOtG1xtw/wM3h 1ctob4WXoRdwZcHzFAsDZoLjrdkSPcArMDcLeNcThdcsex33WPT+Toexlo6ILnPi aWalbYwymW7jybV6OsN9T+ENN+6gIPGIHcJlLvL26slXgvrxfZXL4gHY0yOgsmew 1b63J9MfIFNrZOYT4kXR1iMPCloeTqLzwbNuNI+rPjzIVLAiAEUp6WruCsEY37l0 +wcq+L38ZnC1fWqP3DdnsYhTFbU0cuqbDhQpyvLMCV0kRCKcd8ifoe4BcUdhcHRe edgLdRPmqu/rp9EpNPQ1UFWcmQ1brSXWH5J4nWlx1Ay31Fqu6lgJvGfIq/LphT5Q kJ+uPq4sUFnttPYwolNcnRHjXPTdn8/a4KdrNm7k1uGXek2NgQhy6gBkR68Ii4hX dpD/Os7d5WP3AZY7sVsIpJ2vDR37+s1s/MOWoFz5z9cLsItiErt9EgNclNagwXzS 0KHohQrPWLr5MTPzG7ELJpfZVks8ej5AlY9TONpIcqahGvWuWMo= =g0cP -----END PGP SIGNATURE----- --NDin8bjvE/0mNLFQ-- --===============8807342266481237102== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============8807342266481237102==--