Re: [PATCH v2 6/9] arm64: bcmbca: Make BCM4908 drivers depend on ARCH_BCMBCA

From: Florian Fainelli <f.fainelli@gmail.com>
To: "Rafał Miłecki" <rafal@milecki.pl>,
	"William Zhang" <william.zhang@broadcom.com>
Cc: Linux ARM List <linux-arm-kernel@lists.infradead.org>,
	joel.peshkin@broadcom.com,
	Broadcom Kernel List <bcm-kernel-feedback-list@broadcom.com>,
	dan.beygelman@broadcom.com, anand.gore@broadcom.com,
	kursad.oney@broadcom.com, krzysztof.kozlowski@linaro.org,
	Guenter Roeck <linux@roeck-us.net>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Miquel Raynal <miquel.raynal@bootlin.com>,
	"David S. Miller" <davem@davemloft.net>,
	Rob Herring <robh@kernel.org>,
	Kishon Vijay Abraham I <kishon@ti.com>,
	Vinod Koul <vkoul@kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Wim Van Sebroeck <wim@linux-watchdog.org>,
	linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mtd@lists.infradead.org, netdev@vger.kernel.org,
	linux-pci@vger.kernel.org, linux-phy@lists.infradead.org,
	linux-gpio@vger.kernel.org, linux-mips@vger.kernel.org,
	linux-serial@vger.kernel.org, linux-watchdog@vger.kernel.org
Subject: Re: [PATCH v2 6/9] arm64: bcmbca: Make BCM4908 drivers depend on ARCH_BCMBCA
Date: Thu, 28 Jul 2022 12:22:12 -0700	[thread overview]
Message-ID: <db9560c1-7fc7-405e-bee1-3827a943b712@gmail.com> (raw)
In-Reply-To: <63797827553783061a0ad5e897ed6538@milecki.pl>

On 7/27/22 05:31, Rafał Miłecki wrote:
> On 2022-07-25 07:53, William Zhang wrote:
>> With Broadcom Broadband arch ARCH_BCMBCA supported in the kernel, this
>> patch series migrate the ARCH_BCM4908 symbol to ARCH_BCMBCA. Hence
>> replace ARCH_BCM4908 with ARCH_BCMBCA in subsystem Kconfig files.
>>
>> Signed-off-by: William Zhang <william.zhang@broadcom.com>
>> Acked-by: Guenter Roeck <linux@roeck-us.net> (for watchdog)
>> Acked-by: Bjorn Helgaas <bhelgaas@google.com> (for drivers/pci)
> 
> I still think it may be a bad idea for all below drivers. Please see my
> previous e-mail:
> Re: [RESEND PATCH 6/9] arm64: bcmbca: Make BCM4908 drivers depend on ARCH_BCMBCA
> https://lore.kernel.org/linux-arm-kernel/eee8c85652e6dac69420a876d03f67c4@milecki.pl/
> 
> I think we should:
> 1. Keep ARCH_BCM4908 for 4908 specific drivers (e.g. mtd, pinctrl, net)
> 2. Use ARCH_BCMBCA for more generic drivers (e.g. I2C, PCI,serial, WD)

IMHO here is no point in keeping an ARCH_BCM4908 anymore when the whole point of the patch series is to do a broad conversion of ARCH_BCM4908 into ARCH_BCMBCA. Even if some of the drivers are considered or thought to be 4908-specific, this is not going to be an issue in practice because there ought to be appropriate compatible strings such that even if you built a 4908-specific driver into a generic ARCH_BCMCA kernel, the actual probing would only happen on 4908.

Now let us flip it the other way round, let's say we keep ARCH_BCM4908 as a sub-arch of ARCH_BCMBCA, then this sets a precedent for adding more and more of those ARCH_BCM4906, ARCH_BCM4912 etc. etc to future kernels under the same reasons that we might want to gate certain drivers to certain sub-arches. But what good does that do?

At some point we got to make it simple for the users, and the simplest way is to have ARCH_BCMBCA only and let DT dictate the device specific probing.
-- 
Florian