From: Alan Stern <stern@rowland.harvard.edu>
To: Niklas Schnelle <schnelle@linux.ibm.com>
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, 3 Jan 2022 11:15:16 -0500 [thread overview]
Message-ID: <YdMhFKOdBsDvFStt@rowland.harvard.edu> (raw)
In-Reply-To: <5a271c9e80ee394ecb41297e66d687e035a823ce.camel@linux.ibm.com>
On Mon, Jan 03, 2022 at 12:35:45PM +0100, Niklas Schnelle wrote:
> 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:
> > > > > 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.
The general preference in the kernel is to avoid sprinkling #ifdef's
throughout function definitions, and instead encapsulate their effects
with macros or inline functions -- like this.
> 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.
To help prevent that, we can add
#undef UHCI_IN
#undef UHCI_OUT
at the end of this section.
> > 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.
I definitely would not rely on it.
Alan Stern
next prev parent reply other threads:[~2022-01-03 16:15 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
2022-01-03 16:15 ` Alan Stern [this message]
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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