From: Johan Hovold <firstname.lastname@example.org> To: Linus Walleij <email@example.com> Cc: Johan Hovold <firstname.lastname@example.org>, Marc Zyngier <email@example.com>, linux-usb <firstname.lastname@example.org>, "open list:GPIO SUBSYSTEM" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, Bartosz Golaszewski <firstname.lastname@example.org>, Greg Kroah-Hartman <email@example.com>, firstname.lastname@example.org Subject: Re: [PATCH 0/4] USB: ftdio_sio: GPIO validity fixes Date: Wed, 9 Dec 2020 16:42:21 +0100 [thread overview] Message-ID: <X9DwXS2xaiOs033B@localhost> (raw) In-Reply-To: <CACRpkdZ06vWY+mqR7bYd_WcEM6+N6v5GgTAYhr0p0KkNLa3Qnw@mail.gmail.com> On Wed, Dec 09, 2020 at 10:20:38AM +0100, Linus Walleij wrote: > On Mon, Dec 7, 2020 at 4:48 PM Johan Hovold <email@example.com> wrote: > > On Mon, Dec 07, 2020 at 03:34:23PM +0000, Marc Zyngier wrote: > > > > If they claim that their lines are available, and then refuse to > > > let the user play with it, that's just a bug willing to be fixed. > > > > My point was that this is how *all* gpio drivers work, and that muxing > > is somewhat orthogonal to the gpio controller implementation. > > This is true. It's because it is orthogonal that the separate subsystem > for pin control including pin muxing exists. > > Should I be really overly picky, the drivers that can mux lines like > this should be implementing the pin control mux driver side as > well just to make Linux aware of this. But if the muxing cannot > be changed by the kernel (albeit with special tools) then it would > be pretty overengineered for this case. Things would be much > easier if this wasn't some flashing configuration but more of a > runtime thing (which is kind of the implicit assumption in pin > control land). We'd still have problem of how to configure these hot-pluggable devices at runtime, so it's not necessarily easier. If I remember correctly the xr_serial driver under review is doing something like muxing at runtime, but by simply having whichever interface (tty or gpio) that claims the resource first implicitly set the mux configuration. I have to revisit that. > We don't really have many drivers that are "muxable by > (intrusive) flashing" as opposed to "muxable by setting some > bits" so in that way these FTDI drivers and siblings are special. Yeah, but the gpio-reserved-range (valid-mask) feature which Marc used comes close here. Johan
prev parent reply other threads:[~2020-12-09 15:42 UTC|newest] Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-12-04 16:47 Marc Zyngier 2020-12-04 16:47 ` [PATCH 1/4] gpiolib: cdev: Flag invalid GPIOs as used Marc Zyngier 2020-12-07 14:16 ` Johan Hovold 2020-12-07 14:59 ` Marc Zyngier 2020-12-09 9:25 ` Linus Walleij 2020-12-04 16:47 ` [PATCH 2/4] USB: serial: ftdi_sio: Report the valid GPIO lines to gpiolib Marc Zyngier 2020-12-09 9:28 ` Linus Walleij 2020-12-04 16:47 ` [PATCH 3/4] USB: serial: ftdi_sio: Log the CBUS GPIO validity Marc Zyngier 2020-12-07 14:29 ` Johan Hovold 2020-12-07 15:00 ` Marc Zyngier 2020-12-07 15:19 ` Johan Hovold 2020-12-09 9:35 ` Linus Walleij 2020-12-09 17:05 ` Johan Hovold 2020-12-09 17:39 ` Johan Hovold 2020-12-04 16:47 ` [PATCH 4/4] USB: serial: ftdi_sio: Drop GPIO line checking dead code Marc Zyngier 2020-12-07 9:55 ` [PATCH 0/4] USB: ftdio_sio: GPIO validity fixes Andy Shevchenko 2020-12-07 14:01 ` Johan Hovold 2020-12-07 14:41 ` Marc Zyngier 2020-12-07 15:08 ` Johan Hovold 2020-12-07 15:34 ` Marc Zyngier 2020-12-07 15:49 ` Johan Hovold 2020-12-09 9:20 ` Linus Walleij 2020-12-09 15:42 ` Johan Hovold [this message]
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