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From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: Martijn Coenen <maco@android.com>,
	Andy Gross <andy.gross@linaro.org>,
	David Brown <david.brown@linaro.org>,
	Mimi Zohar <zohar@linux.vnet.ibm.com>,
	Stephen Boyd <sboyd@kernel.org>,
	Vikram Mulukutla <markivx@codeaurora.org>,
	Arve Hj?nnev?g <arve@android.com>, Todd Kjos <tkjos@android.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-security-module@vger.kernel.org,
	Chris Wright <chrisw@sous-sol.org>,
	David Howells <dhowells@redhat.com>,
	Alan Cox <alan@linux.intel.com>,
	Kees Cook <keescook@chromium.org>,
	Hans de Goede <hdegoede@redhat.com>,
	Darren Hart <dvhart@infradead.org>,
	Andy Shevchenko <andy@infradead.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
	platform-driver-x86@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	Peter Jones <pjones@redhat.com>, Dave Olsthoorn <dave@bewaar.me>,
	Will Deacon <will.deacon@arm.com>,
	Andy Lutomirski <luto@kernel.org>,
	Matt Fleming <matt@codeblueprint.co.uk>,
	Josh Triplett <josh@joshtriplett.org>,
	dmitry.torokhov@gmail.com, mfuzzey@parkeon.com,
	Kalle Valo <kvalo@codeaurora.org>,
	Arend Van Spriel <arend.vanspriel@broadcom.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	nbroeking@me.com, Torsten Duwe <duwe@suse.de>,
	x86@kernel.org, linux-efi <linux-efi@vger.kernel.org>,
	"open list:ANDROID DRIVERS" <devel@driverdev.osuosl.org>,
	linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH v3 2/5] efi: Add embedded peripheral firmware support
Date: Thu, 7 Jun 2018 09:49:50 -0700	[thread overview]
Message-ID: <20180607164950.GP510@tuxbook-pro> (raw)
In-Reply-To: <20180508161037.GE27853@wotan.suse.de>

On Tue 08 May 09:10 PDT 2018, Luis R. Rodriguez wrote:

> On Tue, May 08, 2018 at 03:38:05PM +0000, Luis R. Rodriguez wrote:
> > On Fri, May 04, 2018 at 12:44:37PM -0700, Martijn Coenen wrote:
> > > On Wed, Apr 25, 2018 at 10:55 AM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
[..]
> > > 2) Most of those paths are not mounted by the time the corresponding
> > > drivers are loaded, because pretty much all Android kernels today are
> > > built without module support, and therefore drivers are loaded well
> > > before the firmware partition is mounted
> 
> I've given this some more thought and you can address this with initramfs,
> this is how other Linux distributions are addressing this. One way to
> address this automatically is to scrape the drivers built-in or needed early on
> boot in initamfs and if the driver has a MODULE_FIRMWARE() its respective
> firmware is added to initramfs as well.
> 

That could be done, but it would not change the fact that the
/sys/class/firmware is ABI and you may not break it.


And it doesn't change the fact that the ramdisk would have to be over
100mb to facilitate this.

> If you *don't* use initramfs, then yes you can obviously run into issues
> where your firmware may not be accessible if the driver is somehow loaded
> early.
> 

This is still a problem that lacks a solution.

> > > 3) I think we use _FALLBACK because doing this with uevents is just
> > > the easiest thing to do; our init code has a firmware helper that
> > > deals with this and searches the paths that we care about
> > > 
> > > 2) will change at some point, because Android is moving towards a
> > > model where device-specific peripheral drivers will be loaded as
> > > modules, and since those modules would likely come from the same
> > > partition as the firmware, it's possible that the direct load would
> > > succeed (depending on whether the custom path is configured there or
> > > not). But I don't think we can rely on the direct loader even in those
> > > cases, unless we could configure it with multiple custom paths.
> 
> Using initramfs will help, but because of the custom path needs -- you're
> right, we don't have anything for that yet, its also a bit unclear if
> something nice and clean can be drawn up for it. So perhaps dealing with
> the fallback mechanism is the way to go for this for sure, since we already
> have support for it.
> 
> Just keep in mind that the fallback mechanism costs you about ~13436 bytes.
> 

Remember that putting the firmware in the ramdisk would cost about
10000x (yes, ten thousand times) more ram.

> So, if someone comes up with a clean interface for custom paths I'd love
> to consider it to avoid those 13436 bytes.
> 

Combined with a way of synchronizing this with the availability of the
firmware, this would be a nice thing!

Regards,
Bjorn

  reply	other threads:[~2018-06-07 16:48 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-08 17:40 [PATCH v3 0/5] efi/firmware/platform-x86: Add EFI embedded fw support Hans de Goede
2018-04-08 17:40 ` [PATCH v3 1/5] efi: Export boot-services code and data as debugfs-blobs Hans de Goede
2018-04-16  8:23   ` Ard Biesheuvel
2018-04-24 13:11     ` Hans de Goede
2018-04-23 11:55   ` Greg Kroah-Hartman
2018-04-08 17:40 ` [PATCH v3 2/5] efi: Add embedded peripheral firmware support Hans de Goede
2018-04-16  8:28   ` Ard Biesheuvel
2018-04-24 13:17     ` Hans de Goede
2018-04-17  0:17   ` Luis R. Rodriguez
2018-04-17  8:58     ` Hans de Goede
2018-04-17  9:19     ` Hans de Goede
2018-04-23 21:11   ` Luis R. Rodriguez
2018-04-24 15:09     ` Hans de Goede
2018-04-24 16:07       ` Mimi Zohar
2018-04-24 18:33         ` Hans de Goede
2018-04-24 23:42         ` Luis R. Rodriguez
2018-04-25  5:00           ` Mimi Zohar
2018-04-25 17:55             ` Luis R. Rodriguez
2018-05-04  0:21               ` Luis R. Rodriguez
2018-05-04 15:26                 ` Martijn Coenen
2018-05-04 19:44               ` Martijn Coenen
2018-05-08 15:38                 ` Luis R. Rodriguez
2018-05-08 16:10                   ` Luis R. Rodriguez
2018-06-07 16:49                     ` Bjorn Andersson [this message]
2018-06-07 18:22                       ` Luis R. Rodriguez
2018-06-01 19:23                   ` Luis R. Rodriguez
2018-06-06 20:32                     ` Do Qualcomm drivers use DMA buffers for request_firmware_into_buf()? Luis R. Rodriguez
2018-06-07 16:18                       ` Bjorn Andersson
     [not found]                         ` <CAKv+Gu8+Fq7BD4XD-YCyXzZh0mg6Z2k-0styj0cw6_uZfaqy4Q@mail.gmail.com>
     [not found]                           ` <20180607163308.GA18834@kroah.com>
2018-06-08  6:41                             ` Vlastimil Babka
2018-06-07 16:33             ` [PATCH v3 2/5] efi: Add embedded peripheral firmware support Bjorn Andersson
2018-04-08 17:40 ` [PATCH v3 3/5] platform/x86: Rename silead_dmi to touchscreen_dmi Hans de Goede
2018-04-09  8:07   ` Andy Shevchenko
2018-04-20  0:20     ` Darren Hart
2018-04-08 17:40 ` [PATCH v3 4/5] platform/x86: touchscreen_dmi: Add EFI embedded firmware info support Hans de Goede
2018-04-08 17:40 ` [PATCH v3 5/5] platform/x86: touchscreen_dmi: Add info for the Chuwi Vi8 Plus tablet Hans de Goede
2018-04-09  8:10   ` Andy Shevchenko

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