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Message-ID: <Z4-6-ifsuuKMHimq@apocalypse> Date: Tue, 21 Jan 2025 16:19:22 +0100 From: Andrea della Porta <andrea.porta@...e.com> To: Herve Codina <herve.codina@...tlin.com> Cc: Andrea della Porta <andrea.porta@...e.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Florian Fainelli <florian.fainelli@...adcom.com>, Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>, Lorenzo Pieralisi <lpieralisi@...nel.org>, Krzysztof Wilczynski <kw@...ux.com>, Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, Bjorn Helgaas <bhelgaas@...gle.com>, Linus Walleij <linus.walleij@...aro.org>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Bartosz Golaszewski <brgl@...ev.pl>, Derek Kiernan <derek.kiernan@....com>, Dragan Cvetic <dragan.cvetic@....com>, Arnd Bergmann <arnd@...db.de>, Saravana Kannan <saravanak@...gle.com>, linux-clk@...r.kernel.org, devicetree@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, linux-gpio@...r.kernel.org, Masahiro Yamada <masahiroy@...nel.org>, Stefan Wahren <wahrenst@....net>, Luca Ceresoli <luca.ceresoli@...tlin.com>, Thomas Petazzoni <thomas.petazzoni@...tlin.com>, Andrew Lunn <andrew@...n.ch> Subject: Re: [PATCH v6 08/10] misc: rp1: RaspberryPi RP1 misc driver Hi Herve, On 16:15 Tue 21 Jan , Herve Codina wrote: > Hi Andrea, > > On Tue, 21 Jan 2025 15:49:04 +0100 > Greg Kroah-Hartman <gregkh@...uxfoundation.org> 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 <linux/err.h> > > > > > > > > > +#include <linux/interrupt.h> > > > > > > > > > +#include <linux/irq.h> > > > > > > > > > +#include <linux/irqchip/chained_irq.h> > > > > > > > > > +#include <linux/irqdomain.h> > > > > > > > > > +#include <linux/module.h> > > > > > > > > > +#include <linux/msi.h> > > > > > > > > > +#include <linux/of_platform.h> > > > > > > > > > +#include <linux/pci.h> > > > > > > > > > +#include <linux/platform_device.h> > > > > > > > > > + > > > > > > > > > +#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. Good advice, thanks Herve! Added... Regards, Andrea > > Best regards, > Hervé
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