From: Niklas Schnelle <schnelle@linux.ibm.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Arnd Bergmann <arnd@kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>,
John Garry <john.garry@huawei.com>,
Nick Hu <nickhu@andestech.com>, Greentime Hu <green.hu@gmail.com>,
Vincent Chen <deanbo422@gmail.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>, Guo Ren <guoren@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Mathias Nyman <mathias.nyman@intel.com>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
linux-pci@vger.kernel.org, linux-riscv@lists.infradead.org,
linux-csky@vger.kernel.org, linux-usb@vger.kernel.org
Subject: Re: [RFC 31/32] usb: handle HAS_IOPORT dependencies
Date: Mon, 03 Jan 2022 12:35:45 +0100 [thread overview]
Message-ID: <5a271c9e80ee394ecb41297e66d687e035a823ce.camel@linux.ibm.com> (raw)
In-Reply-To: <Yc86mvCUe2mHCa57@rowland.harvard.edu>
On Fri, 2021-12-31 at 12:15 -0500, Alan Stern wrote:
> On Fri, Dec 31, 2021 at 12:06:24PM +0100, Niklas Schnelle wrote:
> > On Mon, 2021-12-27 at 15:36 -0500, Alan Stern wrote:
> > > On Mon, Dec 27, 2021 at 05:43:16PM +0100, Niklas Schnelle wrote:
> > > > In a future patch HAS_IOPORT=n will result in inb()/outb() and friends
> > > > not being declared. We thus need to guard sections of code calling them
> > > > as alternative access methods with CONFIG_HAS_IOPORT checks. Similarly
> > > > drivers requiring these functions need to depend on HAS_IOPORT.
> > >
> > > A few things in here can be improved.
> > >
> > > > Co-developed-by: Arnd Bergmann <arnd@kernel.org>
> > > > Signed-off-by: Arnd Bergmann <arnd@kernel.org>
> > > > Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> > > > ---
> > > > diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
> > > > index ef08d68b9714..bba320194027 100644
> > > > --- a/drivers/usb/host/pci-quirks.c
> > > > +++ b/drivers/usb/host/pci-quirks.c
> > > > +#ifdef CONFIG_USB_PCI_AMD
> > > > +#if IS_ENABLED(CONFIG_USB_UHCI_HCD) && defined(CONFIG_HAS_IOPORT)
> > >
> > > In the original, the following code will be compiled even if
> > > CONFIG_USB_UHCI_HCD is not enabled. You shouldn't change that.
> >
> > If this was only '#ifdef CONFIG_HAS_IOPORT' we would leave
> > uhci_reset_hc() undeclared in the case where CONFIG_HAS_IOPORT is
> > unset. This function however is also called from uhci-pci.c. That on
> > the other hand is built only if CONFIG_USB_UHCI_HCD is set so if we
> > depend on both config options we can get rid of all calls and have the
> > functions undeclared.
>
> But you changed the guard around the '#include "uhci-pci.c"' line in
> uhci-hcd.c, so uhci-pci.c won't be built if CONFIG_HAS_IOPORT is unset.
> Thus there won't be an undefined function call regardless.
Ah thanks yes that makes sense. I seem to have gotten confused by the
uhci-hcd.c vs uhci-pci.c dependency.
>
> You see, even if the kernel isn't configured to include a UHCI driver,
> it's still important to hand off and disable any PCI UHCI hardware when
> the system starts up. Otherwise you can get all sorts of crazy
> interrupts and DMA from the BIOS.
Thanks for the explanation, this is very helpful to understand the
context.
>
> > > > /*
> > > > * Make sure the controller is completely inactive, unable to
> > > > * generate interrupts or do DMA.
> > > > @@ -1273,7 +1277,8 @@ static void quirk_usb_early_handoff(struct pci_dev *pdev)
> > > > "Can't enable PCI device, BIOS handoff failed.\n");
> > > > return;
> > > > }
> > > > - if (pdev->class == PCI_CLASS_SERIAL_USB_UHCI)
> > > > + if (IS_ENABLED(CONFIG_USB_UHCI_HCD) &&
> > > > + pdev->class == PCI_CLASS_SERIAL_USB_UHCI)
> > > > quirk_usb_handoff_uhci(pdev);
> > >
> > > Same idea here.
> >
> > Hmm, I'm not 100% sure if the IS_ENABLED(CONFIG_USB_UHCI_HCD) depends
> > on some compiler optimizations for it to be ok that
> > uhci_check_and_reset_hc() is not declared in the case where both
> > CONFIG_HAS_IOPORT and CONFIG_USB_UHCI_HCD are unset. Maybe that should
> > be a plain ifdef.
>
> The reasoning should be exactly the same as in the previous case.
Yeah with your above explanation it makes sense that we need to keep
the calls even if CONFIG_USB_UHCI_HCD is not enabled. We're also
handling the CONFIG_HAS_IOPORT=n case in quirk_usb_handoff_uhci()
anyway.
>
> > > > diff --git a/drivers/usb/host/uhci-hcd.h b/drivers/usb/host/uhci-hcd.h
> > > > index 8ae5ccd26753..8e30116b6fd2 100644
> > > > --- a/drivers/usb/host/uhci-hcd.h
> > > > +++ b/drivers/usb/host/uhci-hcd.h
> > > > @@ -586,12 +586,14 @@ static inline int uhci_aspeed_reg(unsigned int reg)
> > > >
> > > > static inline u32 uhci_readl(const struct uhci_hcd *uhci, int reg)
> > > > {
> > > > +#ifdef CONFIG_HAS_IOPORT
> > > > if (uhci_has_pci_registers(uhci))
> > > > return inl(uhci->io_addr + reg);
> > > > - else if (uhci_is_aspeed(uhci))
> > > > +#endif
> > >
> > > Instead of making all these changes (here and in the hunks below), you
> > > can simply modify the definition of uhci_has_pci_registers() so that it
> > > always gives 0 when CONFIG_HAS_IOPORT is N.
> > >
> > > Alan Stern
> >
> > I don't think that works, for example in the hunk you quoted returning
> > 0 from uhci_has_pci_registers() only skips over the inl() at run-time.
> > We're aiming to have inl() undeclared if HAS_IOPORT is unset though.
>
> I see. Do you think the following would be acceptable? Add:
>
> #ifdef CONFIG_HAS_IOPORT
> #define UHCI_IN(x) x
> #define UHCI_OUT(x) x
> #else
> #define UHCI_IN(x) 0
> #define UHCI_OUT(x)
> #endif
>
> and then replace for example inl(uhci->io_addr + reg) with
> UHCI_IN(inl(uhci->io_addr + reg)).
In principle that looks like a valid approach. Not sure this is better
than explicit ifdefs though. With this approach one could add
UHCI_IN()/UHCI_OUT() calls which end up as nops without realizing it as
it would disable any compile time warning for using them without
guarding against CONFIG_HAS_IOPORT being undefined.
>
> The definition of uhci_has_pci_registers() should be updated in any
> case; there's no reason for it to do a runtime check of uhci->io_addr
> when HAS_IOPORT is disabled.
Agree. Interestingly same as with the "if
(IS_ENABLED(CONFIG_HAS_IOPORT))" it seems having
uhci_has_pci_registers() compile-time defined to 0 (I added a
defined(CONFIG_HAS_IOPORT) to it) makes the compiler ignore the missing
inl() decleration already. But I'm not sure if we should rely on that.
next prev parent reply other threads:[~2022-01-03 11:36 UTC|newest]
Thread overview: 108+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-27 16:42 [RFC 00/32] Kconfig: Introduce HAS_IOPORT and LEGACY_PCI options Niklas Schnelle
2021-12-27 16:42 ` [RFC 01/32] Kconfig: introduce and depend on LEGACY_PCI Niklas Schnelle
2021-12-27 17:48 ` Guenter Roeck
2021-12-28 2:09 ` Mauro Carvalho Chehab
2021-12-28 8:21 ` Greg Kroah-Hartman
2021-12-28 9:15 ` Mauro Carvalho Chehab
2021-12-28 10:58 ` Niklas Schnelle
2021-12-28 12:01 ` Greg Kroah-Hartman
2021-12-28 12:54 ` Mauro Carvalho Chehab
2021-12-28 15:06 ` Niklas Schnelle
2021-12-28 17:12 ` Mauro Carvalho Chehab
2021-12-29 11:45 ` Niklas Schnelle
2021-12-29 12:12 ` Mauro Carvalho Chehab
2021-12-29 16:03 ` Bjorn Helgaas
2021-12-29 16:55 ` Niklas Schnelle
2022-01-05 17:42 ` John Garry
2022-01-05 19:47 ` Bjorn Helgaas
2022-01-06 17:41 ` John Garry
2022-01-06 18:14 ` Bjorn Helgaas
2022-01-07 17:16 ` John Garry
2022-01-10 9:34 ` Niklas Schnelle
2021-12-27 16:42 ` [RFC 02/32] Kconfig: introduce HAS_IOPORT option and select it as necessary Niklas Schnelle
2021-12-28 10:08 ` Geert Uytterhoeven
2021-12-29 1:20 ` Michael Schmitz
2021-12-29 3:41 ` Arnd Bergmann
2021-12-29 4:15 ` Michael Schmitz
2021-12-30 1:48 ` Arnd Bergmann
2021-12-30 3:44 ` Michael Schmitz
2021-12-31 11:28 ` Niklas Schnelle
2021-12-31 16:04 ` Arnd Bergmann
2021-12-31 21:55 ` Michael Schmitz
2021-12-28 16:32 ` Mauro Carvalho Chehab
2021-12-27 16:42 ` [RFC 03/32] ACPI: Kconfig: add HAS_IOPORT dependencies Niklas Schnelle
2021-12-27 16:47 ` Rafael J. Wysocki
2021-12-27 17:02 ` Niklas Schnelle
2021-12-27 17:12 ` Rafael J. Wysocki
2021-12-27 17:15 ` Rafael J. Wysocki
2021-12-27 17:43 ` Niklas Schnelle
2021-12-28 15:20 ` Rafael J. Wysocki
2021-12-28 16:31 ` Niklas Schnelle
2021-12-27 16:42 ` [RFC 04/32] parport: PC style parport depends on HAS_IOPORT Niklas Schnelle
2021-12-28 10:14 ` Geert Uytterhoeven
2021-12-28 14:21 ` Niklas Schnelle
2021-12-29 2:58 ` Arnd Bergmann
2021-12-27 16:42 ` [RFC 05/32] char: impi, tpm: depend " Niklas Schnelle
2021-12-28 10:17 ` Geert Uytterhoeven
2021-12-28 12:13 ` Niklas Schnelle
2021-12-27 16:42 ` [RFC 06/32] speakup: Kconfig: add HAS_IOPORT dependencies Niklas Schnelle
2021-12-27 17:52 ` Samuel Thibault
2021-12-27 16:42 ` [RFC 07/32] Input: gameport: add ISA and " Niklas Schnelle
2021-12-27 16:42 ` [RFC 08/32] comedi: Kconfig: add " Niklas Schnelle
2021-12-27 16:42 ` [RFC 09/32] sound: " Niklas Schnelle
2021-12-27 16:42 ` [RFC 10/32] i2c: " Niklas Schnelle
2021-12-28 10:21 ` Geert Uytterhoeven
2021-12-28 12:13 ` Niklas Schnelle
2021-12-27 16:42 ` [RFC 11/32] Input: " Niklas Schnelle
2021-12-28 10:23 ` Geert Uytterhoeven
2021-12-27 16:42 ` [RFC 12/32] iio: adc: " Niklas Schnelle
2021-12-28 10:32 ` Geert Uytterhoeven
2021-12-28 12:50 ` Niklas Schnelle
2021-12-28 17:01 ` Jonathan Cameron
2022-01-30 15:05 ` Jonathan Cameron
2021-12-27 16:42 ` [RFC 13/32] hwmon: " Niklas Schnelle
2021-12-27 18:07 ` Guenter Roeck
2021-12-27 16:42 ` [RFC 14/32] leds: " Niklas Schnelle
2021-12-27 16:43 ` [RFC 15/32] media: " Niklas Schnelle
2021-12-27 16:43 ` [RFC 16/32] misc: handle " Niklas Schnelle
2021-12-28 8:15 ` Greg Kroah-Hartman
2021-12-27 16:43 ` [RFC 17/32] net: Kconfig: add " Niklas Schnelle
2021-12-27 17:28 ` Marc Kleine-Budde
2021-12-27 16:43 ` [RFC 18/32] pcmcia: " Niklas Schnelle
2021-12-27 18:41 ` Dominik Brodowski
2021-12-27 16:43 ` [RFC 19/32] platform: " Niklas Schnelle
2021-12-27 16:43 ` [RFC 20/32] pnp: " Niklas Schnelle
2021-12-27 16:43 ` [RFC 21/32] power: " Niklas Schnelle
2021-12-27 16:43 ` [RFC 22/32] video: handle " Niklas Schnelle
2021-12-27 16:43 ` [RFC 23/32] rtc: Kconfig: add " Niklas Schnelle
2021-12-27 16:43 ` [RFC 24/32] scsi: " Niklas Schnelle
2021-12-28 10:40 ` Geert Uytterhoeven
2021-12-27 16:43 ` [RFC 25/32] watchdog: " Niklas Schnelle
2021-12-27 18:03 ` Guenter Roeck
2021-12-28 9:58 ` Niklas Schnelle
2021-12-27 16:43 ` [RFC 26/32] drm: handle " Niklas Schnelle
2022-01-03 6:11 ` Gerd Hoffmann
2021-12-27 16:43 ` [RFC 27/32] PCI/sysfs: make I/O resource depend on HAS_IOPORT Niklas Schnelle
2021-12-27 22:04 ` Bjorn Helgaas
2021-12-27 16:43 ` [RFC 28/32] PCI: make quirk using inw() " Niklas Schnelle
2021-12-27 22:33 ` Bjorn Helgaas
2021-12-28 15:25 ` Niklas Schnelle
2021-12-28 16:35 ` Bjorn Helgaas
2021-12-28 16:52 ` Niklas Schnelle
2021-12-28 17:28 ` Bjorn Helgaas
2021-12-27 16:43 ` [RFC 29/32] firmware: dmi-sysfs: handle HAS_IOPORT dependencies Niklas Schnelle
2021-12-27 16:43 ` [RFC 30/32] /dev/port: don't compile file operations without CONFIG_DEVPORT Niklas Schnelle
2021-12-28 8:17 ` Greg Kroah-Hartman
2021-12-29 10:25 ` Niklas Schnelle
2021-12-29 10:38 ` Greg Kroah-Hartman
2021-12-30 16:19 ` Arnd Bergmann
2021-12-27 16:43 ` [RFC 31/32] usb: handle HAS_IOPORT dependencies Niklas Schnelle
2021-12-27 20:36 ` Alan Stern
2021-12-31 11:06 ` Niklas Schnelle
2021-12-31 17:15 ` Alan Stern
2022-01-03 11:35 ` Niklas Schnelle [this message]
2022-01-03 16:15 ` Alan Stern
2021-12-27 16:43 ` [RFC 32/32] asm-generic/io.h: drop inb() etc for HAS_IOPORT=n Niklas Schnelle
2022-01-06 17:45 ` [RFC 00/32] Kconfig: Introduce HAS_IOPORT and LEGACY_PCI options John Garry
2022-01-07 7:21 ` Niklas Schnelle
2022-01-07 16:57 ` John Garry
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