Re: [PATCH 0/5] gpiolib: Handle immutable irq_chip structures

From: Marc Zyngier <maz@kernel.org>
To: Thierry Reding <thierry.reding@gmail.com>
Cc: linux-kernel@vger.kernel.org,
	Linus Walleij <linus.walleij@linaro.org>,
	Bartosz Golaszewski <brgl@bgdev.pl>,
	Joey Gouly <joey.gouly@arm.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Hector Martin <marcan@marcan.st>, Sven Peter <sven@svenpeter.dev>,
	Alyssa Rosenzweig <alyssa@rosenzweig.io>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Andy Gross <agross@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-gpio@vger.kernel.org, linux-tegra@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-arm-msm@vger.kernel.org, kernel-team@android.com
Subject: Re: [PATCH 0/5] gpiolib: Handle immutable irq_chip structures
Date: Fri, 04 Mar 2022 17:19:17 +0000	[thread overview]
Message-ID: <87ilst1vqi.wl-maz@kernel.org> (raw)
In-Reply-To: <371a530ea9ae8c58bf13ac16d1f2cd3c@kernel.org>

On Thu, 24 Feb 2022 17:42:02 +0000,
Marc Zyngier <maz@kernel.org> wrote:
> 
> On 2022-02-24 16:40, Thierry Reding wrote:
> > On Wed, Feb 23, 2022 at 03:44:00PM +0000, Marc Zyngier wrote:
> >> I recently realised that the gpiolib play ugly tricks on the
> >> unsuspecting irq_chip structures by patching the callbacks.
> >> 
> >> Not only this breaks when an irq_chip structure is made const (which
> >> really should be the default case), but it also forces this structure
> >> to be copied at nauseam for each instance of the GPIO block, which is
> >> a waste of memory.
> >> 
> >> My current approach is to add a new irq_chip flag (IRQCHIP_IMMUTABLE)
> >> which does what it says on the tin: don't you dare writing there.
> >> Gpiolib is further updated not to install its own callbacks, and it
> >> becomes the responsibility of the driver to call into the gpiolib when
> >> required. This is similar to what we do for other subsystems such as
> >> PCI-MSI.
> >> 
> >> 3 drivers are updated to this new model: M1, QC and Tegra, as I
> >> actively use them (though Tegra is hosed at the moment), keeping a
> > 
> > Hosed in what way? Anything I can help with?
> 
> Tegra186 doesn't boot as host1x is been broken since -rc1.
> 
> I have been carrying this[1] patch which has been in -next for
> some time, but still not merged AFAICS.

Looks like it finally made it -rc6.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.