From: Tomi Valkeinen <tomi.valkeinen@ti.com> To: linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 11/11] ARM: versatile: move CLCD configuration to device tree Date: Wed, 24 Feb 2016 12:06:21 +0000 [thread overview] Message-ID: <56CD9CBD.5010106@ti.com> (raw) In-Reply-To: <CAFEAcA-Y7rE_9CiOphgmae3FDApRznoBS7vsVN_+9hBqvAzEEA@mail.gmail.com> [-- Attachment #1: Type: text/plain, Size: 2336 bytes --] On 23/02/16 15:49, Peter Maydell wrote: > On 23 February 2016 at 12:45, Tomi Valkeinen <tomi.valkeinen@ti.com> wrote: >> So, true, there's probing going on, but it's all board specific, >> requiring a board specific driver to support it in the kernel. And I >> think that makes the bootloader much better place for supporting it. > > This doesn't seem to me like a reason to put the requirement > in the bootloader. A huge part of the purpose of the kernel > is to support the hardware (whether that's completely generic > and probeable, like PCI, or generic but not probeable, or > completely specific to a particular board). The kernel has to > support the hardware, and just because it happens to be board > specific hardware rather than generic hardware doesn't seem to > me to imply that the kernel gets to drop part of its core purpose. The thing here is, the kernel doesn't have to support the hardware (the probing method). The kernel _has_ to support the display controller and the panels, but the probing could as well be done in the bootloader. It would work fine, and it would be a cleaner solution that what's being proposed so far. >> I think one of the core questions here is: do we want to start adding >> board specific drivers to the kernel, instead of dealing with it in the >> bootloader when possible? My understanding is that we've been trying to >> reduce board specific code from the kernel. > > I think there's a difference between "reduce board specific code > in the kernel by replacing it with the combination of generic > or parameterisable code in the kernel plus a kernel data structure > (DT) that supplies the parameterisation needed", and "reduce > board specific code in the kernel by forcing the bootloader to > do the kernel's job for it". Perhaps my phone background affects here, but I see the vendor provided bootloader as the place for board specific custom solutions, and then the kernel doesn't have to deal with those if at all possible. With an open source generic bootloader like u-boot that doesn't exactly hold, though, as the custom solutions will still pile up in a common project. Anyway, as discussed in the thread, I'm fine with having a kernel driver for this, as the display boards for Versatile are an external device. Tomi [-- Attachment #2: OpenPGP digital signature --] [-- Type: application/pgp-signature, Size: 819 bytes --]
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From: tomi.valkeinen@ti.com (Tomi Valkeinen) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 11/11] ARM: versatile: move CLCD configuration to device tree Date: Wed, 24 Feb 2016 14:06:21 +0200 [thread overview] Message-ID: <56CD9CBD.5010106@ti.com> (raw) In-Reply-To: <CAFEAcA-Y7rE_9CiOphgmae3FDApRznoBS7vsVN_+9hBqvAzEEA@mail.gmail.com> On 23/02/16 15:49, Peter Maydell wrote: > On 23 February 2016 at 12:45, Tomi Valkeinen <tomi.valkeinen@ti.com> wrote: >> So, true, there's probing going on, but it's all board specific, >> requiring a board specific driver to support it in the kernel. And I >> think that makes the bootloader much better place for supporting it. > > This doesn't seem to me like a reason to put the requirement > in the bootloader. A huge part of the purpose of the kernel > is to support the hardware (whether that's completely generic > and probeable, like PCI, or generic but not probeable, or > completely specific to a particular board). The kernel has to > support the hardware, and just because it happens to be board > specific hardware rather than generic hardware doesn't seem to > me to imply that the kernel gets to drop part of its core purpose. The thing here is, the kernel doesn't have to support the hardware (the probing method). The kernel _has_ to support the display controller and the panels, but the probing could as well be done in the bootloader. It would work fine, and it would be a cleaner solution that what's being proposed so far. >> I think one of the core questions here is: do we want to start adding >> board specific drivers to the kernel, instead of dealing with it in the >> bootloader when possible? My understanding is that we've been trying to >> reduce board specific code from the kernel. > > I think there's a difference between "reduce board specific code > in the kernel by replacing it with the combination of generic > or parameterisable code in the kernel plus a kernel data structure > (DT) that supplies the parameterisation needed", and "reduce > board specific code in the kernel by forcing the bootloader to > do the kernel's job for it". Perhaps my phone background affects here, but I see the vendor provided bootloader as the place for board specific custom solutions, and then the kernel doesn't have to deal with those if at all possible. With an open source generic bootloader like u-boot that doesn't exactly hold, though, as the custom solutions will still pile up in a common project. Anyway, as discussed in the thread, I'm fine with having a kernel driver for this, as the display boards for Versatile are an external device. Tomi -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: OpenPGP digital signature URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20160224/b8465d20/attachment.sig>
next prev parent reply other threads:[~2016-02-24 12:06 UTC|newest] Thread overview: 145+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-02-04 14:04 [PATCH 00/11] CLCD Nomadik+Versatile support Linus Walleij 2016-02-04 14:04 ` Linus Walleij 2016-02-04 14:04 ` [PATCH 01/11] video: ARM CLCD: backlight support for OF Linus Walleij 2016-02-04 14:04 ` Linus Walleij 2016-02-04 14:04 ` [PATCH 02/11] video: ARM CLCD: support DT signal inversion flags Linus Walleij 2016-02-04 14:04 ` Linus Walleij 2016-02-17 18:10 ` [02/11] " Ray Jui 2016-02-17 18:10 ` Ray Jui 2016-02-19 8:46 ` Linus Walleij 2016-02-19 8:46 ` Linus Walleij 2016-02-20 1:23 ` Ray Jui 2016-02-20 1:23 ` Ray Jui 2016-02-20 11:46 ` Linus Walleij 2016-02-20 11:46 ` Linus Walleij 2016-02-04 14:04 ` [PATCH 03/11] video: ARM CLCD: support pads connected in reverse order Linus Walleij 2016-02-04 14:04 ` Linus Walleij 2016-02-04 14:04 ` [PATCH 04/11] video: ARM CLCD: support Nomadik variant Linus Walleij 2016-02-04 14:04 ` Linus Walleij 2016-02-04 14:04 ` [PATCH 05/11] video: ARM CLCD: add special board and panel hooks for Nomadik Linus Walleij 2016-02-04 14:04 ` Linus Walleij 2016-02-04 14:04 ` [PATCH 06/11] Documentation/DT: add blurb for IB2 syscon to Versatile Linus Walleij 2016-02-04 14:04 ` Linus Walleij 2016-02-04 14:04 ` [PATCH 07/11] Documentation/DT: add Versatile display bindings Linus Walleij 2016-02-04 14:04 ` Linus Walleij 2016-02-17 9:11 ` Tomi Valkeinen 2016-02-17 9:11 ` Tomi Valkeinen 2016-02-18 20:48 ` Linus Walleij 2016-02-18 20:48 ` Linus Walleij 2016-02-04 14:04 ` [PATCH 08/11] video: ARM CLCD: add special panel hook for Versatiles Linus Walleij 2016-02-04 14:04 ` Linus Walleij 2016-02-04 14:04 ` [PATCH 09/11] ARM: PB11MPCore: define a standard VGA panel Linus Walleij 2016-02-04 14:04 ` Linus Walleij 2016-02-04 14:04 ` [PATCH 10/11] ARM: PB1176: " Linus Walleij 2016-02-04 14:04 ` Linus Walleij 2016-02-04 14:04 ` [PATCH 11/11] ARM: versatile: move CLCD configuration to device tree Linus Walleij 2016-02-04 14:04 ` Linus Walleij 2016-02-17 9:09 ` Tomi Valkeinen 2016-02-17 9:09 ` Tomi Valkeinen 2016-02-17 9:41 ` Russell King - ARM Linux 2016-02-17 9:41 ` Russell King - ARM Linux 2016-02-17 16:17 ` Linus Walleij 2016-02-17 16:17 ` Linus Walleij 2016-02-17 21:32 ` Russell King - ARM Linux 2016-02-17 21:32 ` Russell King - ARM Linux 2016-02-18 11:52 ` Tomi Valkeinen 2016-02-18 11:52 ` Tomi Valkeinen 2016-02-18 13:12 ` Russell King - ARM Linux 2016-02-18 13:12 ` Russell King - ARM Linux 2016-02-18 13:37 ` Tomi Valkeinen 2016-02-18 13:37 ` Tomi Valkeinen 2016-02-18 20:31 ` Linus Walleij 2016-02-18 20:31 ` Linus Walleij [not found] ` <56C5B080.9090007-l0cyMroinI0@public.gmane.org> 2016-02-21 22:39 ` Linus Walleij 2016-02-21 22:39 ` Linus Walleij 2016-02-21 22:39 ` Linus Walleij [not found] ` <CACRpkdaXFUCR5=5mS28_4Dx_LfzqV13zwT=vVeJwuOzm_rGRBQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2016-02-22 15:41 ` Tomi Valkeinen 2016-02-22 15:41 ` Tomi Valkeinen 2016-02-22 15:41 ` Tomi Valkeinen [not found] ` <56CB2C31.5040703-l0cyMroinI0@public.gmane.org> 2016-02-22 15:54 ` Linus Walleij 2016-02-22 15:54 ` Linus Walleij 2016-02-22 15:54 ` Linus Walleij 2016-02-23 9:08 ` Linus Walleij 2016-02-23 9:08 ` Linus Walleij 2016-02-23 9:34 ` Arnd Bergmann 2016-02-23 9:34 ` Arnd Bergmann 2016-02-23 10:10 ` Linus Walleij 2016-02-23 10:10 ` Linus Walleij 2016-02-23 11:22 ` Arnd Bergmann 2016-02-23 11:22 ` Arnd Bergmann 2016-02-23 13:00 ` Tomi Valkeinen 2016-02-23 13:00 ` Tomi Valkeinen 2016-02-23 13:16 ` Linus Walleij 2016-02-23 13:16 ` Linus Walleij 2016-02-23 13:38 ` Tomi Valkeinen 2016-02-23 13:38 ` Tomi Valkeinen 2016-02-24 10:53 ` Russell King - ARM Linux 2016-02-24 10:53 ` Russell King - ARM Linux 2016-02-24 11:35 ` Tomi Valkeinen 2016-02-24 11:35 ` Tomi Valkeinen 2016-02-25 14:04 ` Linus Walleij 2016-02-25 14:04 ` Linus Walleij 2016-02-25 16:08 ` Arnd Bergmann 2016-02-25 16:08 ` Arnd Bergmann 2016-02-25 16:22 ` Russell King - ARM Linux 2016-02-25 16:22 ` Russell King - ARM Linux 2016-02-25 16:45 ` Tomi Valkeinen 2016-02-25 16:45 ` Tomi Valkeinen 2016-02-25 16:57 ` Russell King - ARM Linux 2016-02-25 16:57 ` Russell King - ARM Linux 2016-02-25 19:30 ` Linus Walleij 2016-02-25 19:30 ` Linus Walleij 2016-02-26 10:47 ` Tomi Valkeinen 2016-02-26 10:47 ` Tomi Valkeinen 2016-03-05 16:57 ` Linus Walleij 2016-03-05 16:57 ` Linus Walleij 2016-03-07 7:36 ` Tomi Valkeinen 2016-03-07 7:36 ` Tomi Valkeinen 2016-02-25 19:32 ` Linus Walleij 2016-02-25 19:32 ` Linus Walleij 2016-02-23 9:58 ` Tomi Valkeinen 2016-02-23 9:58 ` Tomi Valkeinen 2016-02-23 10:32 ` Adam Ford 2016-02-23 10:32 ` Adam Ford 2016-02-23 10:59 ` Pantelis Antoniou 2016-02-23 10:59 ` Pantelis Antoniou 2016-02-23 11:56 ` Peter Maydell 2016-02-23 11:56 ` Peter Maydell 2016-02-23 12:01 ` Russell King - ARM Linux 2016-02-23 12:01 ` Russell King - ARM Linux 2016-02-23 13:45 ` Tom Rini 2016-02-23 13:45 ` Tom Rini 2016-02-23 12:45 ` Tomi Valkeinen 2016-02-23 12:45 ` Tomi Valkeinen 2016-02-23 13:49 ` Peter Maydell 2016-02-23 13:49 ` Peter Maydell 2016-02-24 12:06 ` Tomi Valkeinen [this message] 2016-02-24 12:06 ` Tomi Valkeinen 2016-02-24 10:46 ` Russell King - ARM Linux 2016-02-24 10:46 ` Russell King - ARM Linux 2016-02-24 11:21 ` Tomi Valkeinen 2016-02-24 11:21 ` Tomi Valkeinen 2016-02-24 11:35 ` Russell King - ARM Linux 2016-02-24 11:35 ` Russell King - ARM Linux 2016-02-24 11:47 ` Tomi Valkeinen 2016-02-24 11:47 ` Tomi Valkeinen 2016-02-24 12:13 ` Pantelis Antoniou 2016-02-24 12:13 ` Pantelis Antoniou 2016-02-25 13:43 ` Linus Walleij 2016-02-25 13:43 ` Linus Walleij 2016-02-25 13:56 ` Tomi Valkeinen 2016-02-25 13:56 ` Tomi Valkeinen 2016-02-25 14:35 ` Pantelis Antoniou 2016-02-25 14:35 ` Pantelis Antoniou 2016-02-25 15:36 ` Linus Walleij 2016-02-25 15:36 ` Linus Walleij 2016-02-25 15:40 ` Pantelis Antoniou 2016-02-25 15:40 ` Pantelis Antoniou 2016-02-23 13:08 ` Linus Walleij 2016-02-23 13:08 ` Linus Walleij 2016-02-15 23:34 ` [PATCH 00/11] CLCD Nomadik+Versatile support Linus Walleij 2016-02-15 23:34 ` Linus Walleij 2016-02-16 13:29 ` Tomi Valkeinen 2016-02-16 13:29 ` Tomi Valkeinen 2016-02-16 22:30 ` Linus Walleij 2016-02-16 22:30 ` Linus Walleij
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