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Message-ID: <aa679655-290e-4d19-9195-1a581431b9e6@suse.de>
Date: Mon, 21 Oct 2024 12:58:36 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Arnd Bergmann <arnd@...db.de>, Niklas Schnelle <schnelle@...ux.ibm.com>,
Brian Cain <bcain@...cinc.com>, Marcel Holtmann <marcel@...tmann.org>,
Luiz Augusto von Dentz <luiz.dentz@...il.com>,
Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Dave Airlie <airlied@...il.com>,
Simona Vetter <simona@...ll.ch>, Dave Airlie <airlied@...hat.com>,
Gerd Hoffmann <kraxel@...hat.com>, Lucas De Marchi
<lucas.demarchi@...el.com>,
Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jirislaby@...nel.org>, "Maciej W. Rozycki" <macro@...am.me.uk>,
Heiko Carstens <hca@...ux.ibm.com>
Cc: linux-kernel@...r.kernel.org, linux-hexagon@...r.kernel.org,
linux-bluetooth@...r.kernel.org, dri-devel@...ts.freedesktop.org,
virtualization@...ts.linux.dev, spice-devel@...ts.freedesktop.org,
intel-xe@...ts.freedesktop.org, linux-serial@...r.kernel.org,
Linux-Arch <linux-arch@...r.kernel.org>, Arnd Bergmann <arnd@...nel.org>
Subject: Re: [PATCH v8 3/5] drm: handle HAS_IOPORT dependencies
Hi
Am 21.10.24 um 12:08 schrieb Arnd Bergmann:
> On Mon, Oct 21, 2024, at 07:52, Thomas Zimmermann wrote:
>> Am 08.10.24 um 14:39 schrieb Niklas Schnelle:
> d 100644
>>> --- a/drivers/gpu/drm/qxl/Kconfig
>>> +++ b/drivers/gpu/drm/qxl/Kconfig
>>> @@ -2,6 +2,7 @@
>>> config DRM_QXL
>>> tristate "QXL virtual GPU"
>>> depends on DRM && PCI && MMU
>>> + depends on HAS_IOPORT
>> Is there a difference between this style (multiple 'depends on') and the
>> one used for gma500 (&& && &&)?
> No, it's the same. Doing it in one line is mainly useful
> if you have some '||' as well.
>
>>> @@ -105,7 +106,9 @@ static void bochs_vga_writeb(struct bochs_device *bochs, u16 ioport, u8 val)
>>>
>>> writeb(val, bochs->mmio + offset);
>>> } else {
>>> +#ifdef CONFIG_HAS_IOPORT
>>> outb(val, ioport);
>>> +#endif
>> Could you provide empty defines for the out() interfaces at the top of
>> the file?
> That no longer works since there are now __compiletime_error()
> versions of these funcitons. However we can do it more nicely like:
>
> diff --git a/drivers/gpu/drm/tiny/bochs.c b/drivers/gpu/drm/tiny/bochs.c
> index 9b337f948434..034af6e32200 100644
> --- a/drivers/gpu/drm/tiny/bochs.c
> +++ b/drivers/gpu/drm/tiny/bochs.c
> @@ -112,14 +112,12 @@ static void bochs_vga_writeb(struct bochs_device *bochs, u16 ioport, u8 val)
> if (WARN_ON(ioport < 0x3c0 || ioport > 0x3df))
> return;
>
> - if (bochs->mmio) {
> + if (!IS_DEFINED(CONFIG_HAS_IOPORT) || bochs->mmio) {
> int offset = ioport - 0x3c0 + 0x400;
>
> writeb(val, bochs->mmio + offset);
> } else {
> -#ifdef CONFIG_HAS_IOPORT
> outb(val, ioport);
> -#endif
> }
For all functions with such a pattern, could we use:
bool bochs_uses_mmio(bochs)
{
return !IS_DEFINED(CONFIG_HAS_IOPORT) || bochs->mmio
}
void writeb_func()
{
if (bochs_uses_mmio()) {
writeb()
#if CONFIG_HAS_IOPORT
} else {
outb()
#endif
}
}
u8 readb_func()
{
u8 ret = 0xff
if (bochs_uses_mmio()) {
ret = readb()
#if CONFIG_HAS_IOPORT
} else {
ret = inb()
#endif
}
return ret;
}
?
The code in bochs_uses_mmio() could then also print a drm_warn_once if
we have neither MMIO nor I/O ports.
I'd review a separate series for such a change.
> }
>
> @@ -128,16 +126,12 @@ static u8 bochs_vga_readb(struct bochs_device *bochs, u16 ioport)
> if (WARN_ON(ioport < 0x3c0 || ioport > 0x3df))
> return 0xff;
>
> - if (bochs->mmio) {
> + if (!IS_DEFINED(CONFIG_HAS_IOPORT) || bochs->mmio) {
> int offset = ioport - 0x3c0 + 0x400;
>
> return readb(bochs->mmio + offset);
> } else {
> -#ifdef CONFIG_HAS_IOPORT
> return inb(ioport);
> -#else
> - return 0xff;
> -#endif
> }
> }
>
> @@ -145,32 +139,26 @@ static u16 bochs_dispi_read(struct bochs_device *bochs, u16 reg)
> {
> u16 ret = 0;
>
> - if (bochs->mmio) {
> + if (!IS_DEFINED(CONFIG_HAS_IOPORT) || bochs->mmio) {
> int offset = 0x500 + (reg << 1);
>
> ret = readw(bochs->mmio + offset);
> } else {
> -#ifdef CONFIG_HAS_IOPORT
> outw(reg, VBE_DISPI_IOPORT_INDEX);
> ret = inw(VBE_DISPI_IOPORT_DATA);
> -#else
> - ret = 0xffff;
> -#endif
> }
> return ret;
> }
>
> static void bochs_dispi_write(struct bochs_device *bochs, u16 reg, u16 val)
> {
> - if (bochs->mmio) {
> + if (!IS_DEFINED(CONFIG_HAS_IOPORT) || bochs->mmio) {
> int offset = 0x500 + (reg << 1);
>
> writew(val, bochs->mmio + offset);
> } else {
> -#ifdef CONFIG_HAS_IOPORT
> outw(reg, VBE_DISPI_IOPORT_INDEX);
> outw(val, VBE_DISPI_IOPORT_DATA);
> -#endif
> }
> }
>
>> And the in() interfaces could be defined to 0xff[ff].
>>
>> I assume that you don't want to provide such empty macros in the
>> kernel's io.h header?
> That was the original idea many years ago, but Linus rejected
> my pull request for it, so Niklas worked through all drivers
> individually to add the dependencies instead.
I see.
Best regards
Thomas
>
> Arnd
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
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