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bh=X4Q4hJw5c+A/aS0RSQxPiCKAtW+pQN8zj4IF9YAn0J8=; b=S5VkIzWdwIvCY/+i6lnX+FglRqgvtroMLGFdMIXk4BB3QN6KHEDTA8glOOXknkPCEiDWpA 4d4wAPAAzQ4hEdQBk83SsuarvVuDzc8lTIKBcwjbT7pv2XNIy2D41javnOdRc+xuzn2FPo 7Q/61hfQ7ZMU3SmkR2f/PkjvDsKE3P5bkbxdDmsAFBEB1lYv0DVoZ5zYSULze92mmrc7r3 y75Xr2sH0yYNnx2GwIhRvaEFVT7yRQA3TBVSgJMmq/fcCmnyKiwegMu/kL6SKQw1LqPlVS 4g75aDVWjceQCeMejRE//Rufe+0QXXqItevCkqJ59nxCJBjhFY5wYgT8gPGU4g== Date: Tue, 21 Jan 2025 16:15:12 +0100 From: Herve Codina To: Andrea della Porta Cc: Greg Kroah-Hartman , Michael Turquette , Stephen Boyd , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Florian Fainelli , Broadcom internal kernel review list , Lorenzo Pieralisi , Krzysztof Wilczynski , Manivannan Sadhasivam , Bjorn Helgaas , Linus Walleij , Catalin Marinas , Will Deacon , Bartosz Golaszewski , Derek Kiernan , Dragan Cvetic , Arnd Bergmann , Saravana Kannan , linux-clk@vger.kernel.org, devicetree@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-gpio@vger.kernel.org, Masahiro Yamada , Stefan Wahren , Luca Ceresoli , Thomas Petazzoni , Andrew Lunn Subject: Re: [PATCH v6 08/10] misc: rp1: RaspberryPi RP1 misc driver Message-ID: <20250121161512.2a3ac703@bootlin.com> In-Reply-To: <2025012148-unused-winking-7d51@gregkh> References: <550590a5a0b80dd8a0c655921ec0aa41a67c8148.1736776658.git.andrea.porta@suse.com> <2025011722-motocross-finally-e664@gregkh> <2025012143-rippling-rehydrate-581b@gregkh> <2025012157-bonsai-caddie-19b2@gregkh> <2025012148-unused-winking-7d51@gregkh> Organization: Bootlin X-Mailer: Claws Mail 4.3.0 (GTK 3.24.43; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-gpio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-GND-Sasl: herve.codina@bootlin.com Hi Andrea, On Tue, 21 Jan 2025 15:49:04 +0100 Greg Kroah-Hartman wrote: > On Tue, Jan 21, 2025 at 03:38:42PM +0100, Andrea della Porta wrote: > > Hi Greg, > > > > On 15:18 Tue 21 Jan , Greg Kroah-Hartman wrote: > > > On Tue, Jan 21, 2025 at 02:59:21PM +0100, Andrea della Porta wrote: > > > > Hi Greg, > > > > > > > > On 09:48 Tue 21 Jan , Greg Kroah-Hartman wrote: > > > > > On Tue, Jan 21, 2025 at 09:43:37AM +0100, Andrea della Porta wrote: > > > > > > Hi Greg, > > > > > > > > > > > > On 12:47 Fri 17 Jan , Greg Kroah-Hartman wrote: > > > > > > > On Mon, Jan 13, 2025 at 03:58:07PM +0100, Andrea della Porta wrote: > > > > > > > > The RaspberryPi RP1 is a PCI multi function device containing > > > > > > > > peripherals ranging from Ethernet to USB controller, I2C, SPI > > > > > > > > and others. > > > > > > > > > > > > > > > > Implement a bare minimum driver to operate the RP1, leveraging > > > > > > > > actual OF based driver implementations for the on-board peripherals > > > > > > > > by loading a devicetree overlay during driver probe. > > > > > > > > > > > > > > > > The peripherals are accessed by mapping MMIO registers starting > > > > > > > > from PCI BAR1 region. > > > > > > > > > > > > > > > > With the overlay approach we can achieve more generic and agnostic > > > > > > > > approach to managing this chipset, being that it is a PCI endpoint > > > > > > > > and could possibly be reused in other hw implementations. The > > > > > > > > presented approach is also used by Bootlin's Microchip LAN966x > > > > > > > > patchset (see link) as well, for a similar chipset. > > > > > > > > > > > > > > > > For reasons why this driver is contained in drivers/misc, please > > > > > > > > check the links. > > > > > > > > > > > > > > Links aren't always around all the time, please document it here why > > > > > > > this is needed, and then links can "add to" that summary. > > > > > > > > > > > > Ack. > > > > > > > > > > > > > > > > > > > > > This driver is heavily based on downstream code from RaspberryPi > > > > > > > > Foundation, and the original author is Phil Elwell. > > > > > > > > > > > > > > > > Link: https://datasheets.raspberrypi.com/rp1/rp1-peripherals.pdf > > > > > > > > > > > > ... > > > > > > > > > > > > > > diff --git a/drivers/misc/rp1/rp1_pci.c b/drivers/misc/rp1/rp1_pci.c > > > > > > > > new file mode 100644 > > > > > > > > index 000000000000..3e8ba3fa7fd5 > > > > > > > > --- /dev/null > > > > > > > > +++ b/drivers/misc/rp1/rp1_pci.c > > > > > > > > @@ -0,0 +1,305 @@ > > > > > > > > +// SPDX-License-Identifier: GPL-2.0 > > > > > > > > +/* > > > > > > > > + * Copyright (c) 2018-24 Raspberry Pi Ltd. > > > > > > > > + * All rights reserved. > > > > > > > > + */ > > > > > > > > + > > > > > > > > +#include > > > > > > > > +#include > > > > > > > > +#include > > > > > > > > +#include > > > > > > > > +#include > > > > > > > > +#include > > > > > > > > +#include > > > > > > > > +#include > > > > > > > > +#include > > > > > > > > +#include > > > > > > > > + > > > > > > > > +#include "rp1_pci.h" > > > > > > > > > > > > > > Why does a self-contained .c file need a .h file? Please put it all in > > > > > > > here. > > > > > > > > > > > > I agree with you. Indeed, the very first version of this patch had the header > > > > > > file placed inside the .c, but I received concerns about it and some advice to > > > > > > do it differently, as you can see here: > > > > > > https://lore.kernel.org/all/ZtWDpaqUG9d9yPPf@apocalypse/ > > > > > > so I've changed it accordingly in V2. So right now I'm not sure what the > > > > > > acceptable behaviour should be ... > > > > > > > > > > It's a pretty simple rule: > > > > > Only use a .h file if multiple .c files need to see the symbol. > > > > > > > > > > So no .h file is needed here. > > > > > > > > Perfect, I'll revert back that two lines to V1 then. Please be aware > > > > though that this will trigger the following checkpatch warning: > > > > > > > > WARNING: externs should be avoided in .c files > > > > > > Well where are those externs defined at? Shouldn't there be a .h file > > > for them somewhere in the tree if they really are global? > > > > Those symbols are deined in drivers/misc/rp1/rp1-pci.dtbo.S (added by > > this patchset) and created by cmd_wrap_S_dtb in scripts/Makefile.lib. > > They are just placeholders that contains rp1-pci.dtbo as > > a binary blob, in order for the driver (rp1_pci.c) to be able to use > > the binary buffer representing the overlay and address it from the > > driver probe function. > > So there's no other reference from outside rp1_pci.c to those two symbols. > > In comparison, this is the very same approach used by a recently accepted > > patch involving drivers/misc/lan966x_pci.c, which also has the two externs > > in it and triggers the same checkpatch warning. > > Ok, that's fine, checkpatch is just a hint, not a hard-and-fast-rule. > Maybe just to avoid confusion for future readers, you can add a comment as I did for the lan966x: https://elixir.bootlin.com/linux/v6.13-rc3/source/drivers/misc/lan966x_pci.c#L21 This will not avoid the warning but will give an explanation to people looking closer at this checkpatch warning. Best regards, Hervé