From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx4818jR8PUAV1xyzGGsnngv7TMWZK5eiPcIa/4w5mV1J+hZ+1SPdzawd/g82T02JZA0e8xtj ARC-Seal: i=1; a=rsa-sha256; t=1524591616; cv=none; d=google.com; s=arc-20160816; b=doEH4d5VibiCH8x1gAWYEaRop+bvpFB/K9EQu+oKYXc1WKqruh2Vq/87RkUfwgSPlv 6KJ7+eaEJmOM8cAvDMkjEYpoVBtOUUmMGinHkn5/sbNL9L0PwxUS8sEKfu0I22svkouz AVryX1hlwahgdenCALE/goUeWrJX5dDzFCJIoGO84k2TvDnXaEOxA+JYZHAdcm1plIK9 Q42oXK/tQ8gSsTvgLUGiKvHVyXNJrQiRkTUnQ4Pj7k0qB6OXf5iPh8sDowCwuyZ10vmU 7OcVeLBcVQiWMZPE7koSuH0RWanqel+kWH+r5ABPmAfo2O/byQcVANFR5Na4cCCmjEwt 2UKw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=to:references:message-id:content-transfer-encoding:cc:date :in-reply-to:from:subject:mime-version:dkim-signature :arc-authentication-results; bh=Zkc49OAEDlRYDMFwx/TpjYnTa6HphbwmkyzXvaEsNNQ=; b=laIBRBySFEFqM4WptHbSMog8OBzKAYPH1D5lJR1cDmJ+2e8FhovyQBZz0vGHiYxXQP vzgD6tpzRDxjXWykVXJxPbBPhAHnLzKXCVGamiLM/jNXSWAuOrJRYZLiX0D8KcCAXX7F Yvn6Zsr5mgT5dXZ9gcMNABQiK8euUqtQXtQSI9Wbnu88eVo1G4PIvqVKIJngccm9ptDG yHQ9LBagv8fEqg9XDpDArZjpQMzJJCSJD0+A2aQqH64EHaTV+DBOQncIn0mhMP557YZ0 2tNG7Kwrw8yRgfX9wwesBekS2msC4lR6kl1OqDQ1tCsk62ZeUgOFYd62GskHJRDXG5UX wrog== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@goldelico.com header.s=strato-dkim-0002 header.b=oRmqV2n6; spf=neutral (google.com: 2a01:238:20a:202:5301::3 is neither permitted nor denied by best guess record for domain of hns@goldelico.com) smtp.mailfrom=hns@goldelico.com Authentication-Results: mx.google.com; dkim=pass header.i=@goldelico.com header.s=strato-dkim-0002 header.b=oRmqV2n6; spf=neutral (google.com: 2a01:238:20a:202:5301::3 is neither permitted nor denied by best guess record for domain of hns@goldelico.com) smtp.mailfrom=hns@goldelico.com X-RZG-AUTH: :JGIXVUS7cutRB/49FwqZ7WcJeFKiMgPgp8VKxflSZ1P34KBj4Qpw87Wiv9N1ED6Y X-RZG-CLASS-ID: mo00 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Subject: Re: [PATCH 0/7] gnss: add new GNSS subsystem From: "H. Nikolaus Schaller" In-Reply-To: <20180424163458.11947-1-johan@kernel.org> Date: Tue, 24 Apr 2018 19:40:00 +0200 Cc: Greg Kroah-Hartman , Rob Herring , Mark Rutland , Andreas Kemnade , Arnd Bergmann , Pavel Machek , Linux Kernel Mailing List , Discussions about the Letux Kernel , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" Content-Transfer-Encoding: quoted-printable Message-Id: <31CF06C6-D6ED-4930-8D81-12256A518059@goldelico.com> References: <20180424163458.11947-1-johan@kernel.org> To: Johan Hovold X-Mailer: Apple Mail (2.3124) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1598647061282688193?= X-GMAIL-MSGID: =?utf-8?q?1598650178719709255?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Hi Johan, > Am 24.04.2018 um 18:34 schrieb Johan Hovold : >=20 > This series adds a new subsystem for GNSS receivers (e.g. GPS > receivers). Great! >=20 > While GNSS receivers are typically accessed using a UART interface = they > often also support other I/O interfaces such as I2C, SPI and USB, = while > yet other devices use iomem or even some form of remote-processor > messaging (rpmsg). >=20 > The new GNSS subsystem abstracts the underlying interface and provides = a > new "gnss" class type, which exposes a character-device interface = (e.g. > /dev/gnss0) to user space. This allows GNSS receivers to have a > representation in the Linux device model, something which is important > not least for power management purposes and which also allows for easy > detection and (eventually) identification of GNSS devices. >=20 > Note that the character-device interface provides raw access to = whatever > protocol the receiver is (currently) using, such as NMEA 0183, UBX or > SiRF Binary. These protocols are expected to be continued to be = handled > by user space for the time being, even if some hybrid solutions are = also > conceivable (e.g. to have kernel drivers issue management commands). >=20 > This will still allow for better platform integration by allowing GNSS > devices and their resources (e.g. regulators and enable-gpios) to be > described by firmware and managed by kernel drivers rather than > platform-specific scripts and services. >=20 > While the current interface is kept minimal, it could be extended = using > IOCTLs, sysfs or uevents as needs and proper abstraction levels are > identified and determined (e.g. for device and feature = identification). >=20 > Another possible extension is to add generic 1PPS support. would be nice but not first priority. >=20 > I decided to go with a custom character-device interface rather than > pretend that these abstract GNSS devices are still TTY devices (e.g. > /dev/ttyGNSS0). Obviously, modifying line settings or reading modem > control signals does not make any sense for a device using, say, a > USB (not USB-serial) or iomem interface. This also means, however, = that > user space would no longer be able to set the line speed to match a = new > port configuration that can be set using the various GNSS protocols = when > the underlying interface is indeed a UART; instead this would need to = be > taken care of by the driver. >=20 > Also note that writes are always synchronous instead of requiring user > space to call tcdrain() after every command. >=20 > This all seems to work well-enough (e.g. with gpsd), but please let me > know if I've overlooked something which would indeed require a TTY > interface instead. tcgetattr() / tcsetattr() for controlling line disciplines, e.g. stty -icanon =20 > As proof-of-concept I have implemented drivers for receivers based on > two common GNSS chipsets (SiRFstar and u-blox), but due to lack of > hardware these have so far only been tested using mockup devices and a > USB-serial-based GPS device (using out-of-tree code). [ Let me know if > you've got any evalutation kits to spare. ] Ok, those drivers look nice on first glance. BTW: I have refactored our w2sg00x4 driver into a gps-core (still = creating a /dev/GPS0) and a driver using a common API. With that it should almost fit by coping some lines from your serdev = based device drivers. I haven't found time to submit anything, so it is just living (and = working) in our private tree (please ignore w2cbw003 and trs3386 stuff): = http://git.goldelico.com/?p=3Dgta04-kernel.git;a=3Dshortlog;h=3Drefs/heads= /work/letux-base/hns/misc/w2sg-serdev-v6 = http://git.goldelico.com/?p=3Dgta04-kernel.git;a=3Dcommit;h=3D164c13373462= 596cabdd3b5308e5f7d8626a05af >=20 > Finally, note that documentation (including kerneldoc) remains to be > written, but hopefully this will not hinder review given that the > current interfaces are fairly self-describing. I'll apply your patches and try to adjust our w2sg driver. And report issues if they arise. BR and thanks, Nikolaus >=20 > Johan >=20 >=20 > Johan Hovold (7): > gnss: add GNSS receiver subsystem > dt-bindings: add generic gnss binding > gnss: add generic serial driver > dt-bindings: gnss: add u-blox binding > gnss: add driver for u-blox receivers > dt-bindings: gnss: add sirfstar binding > gnss: add driver for sirfstar-based receivers >=20 > .../devicetree/bindings/gnss/gnss.txt | 36 ++ > .../devicetree/bindings/gnss/sirfstar.txt | 38 ++ > .../devicetree/bindings/gnss/u-blox.txt | 31 ++ > .../devicetree/bindings/vendor-prefixes.txt | 4 + > MAINTAINERS | 7 + > drivers/Kconfig | 2 + > drivers/Makefile | 1 + > drivers/gnss/Kconfig | 43 ++ > drivers/gnss/Makefile | 16 + > drivers/gnss/core.c | 385 ++++++++++++++++ > drivers/gnss/serial.c | 288 ++++++++++++ > drivers/gnss/serial.h | 47 ++ > drivers/gnss/sirf.c | 415 ++++++++++++++++++ > drivers/gnss/ubx.c | 133 ++++++ > include/linux/gnss.h | 64 +++ > 15 files changed, 1510 insertions(+) > create mode 100644 Documentation/devicetree/bindings/gnss/gnss.txt > create mode 100644 Documentation/devicetree/bindings/gnss/sirfstar.txt > create mode 100644 Documentation/devicetree/bindings/gnss/u-blox.txt > create mode 100644 drivers/gnss/Kconfig > create mode 100644 drivers/gnss/Makefile > create mode 100644 drivers/gnss/core.c > create mode 100644 drivers/gnss/serial.c > create mode 100644 drivers/gnss/serial.h > create mode 100644 drivers/gnss/sirf.c > create mode 100644 drivers/gnss/ubx.c > create mode 100644 include/linux/gnss.h >=20 > --=20 > 2.17.0 >=20