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. Many thanks, Andrea > > thanks, > > greg k-h
