[PATCH v8 0/5] treewide: Remove I/O port accessors for HAS_IOPORT=n

[PATCH v8 0/5] treewide: Remove I/O port accessors for HAS_IOPORT=n

[Niklas Schnelle]

Hi All,

This is a follow up in my long running effort of making inb()/outb() and
similar I/O port accessors compile-time optional. After initially
sending this as a treewide series with the latest revision at[0]
we switched to per subsystem series. Now though as we're left with only
5 patches left I'm going back to a single series with Arnd planning
to take this via the the asm-generic tree.

This series may also be viewed for your convenience on my git.kernel.org
tree[1] under the b4/has_ioport branch. As for compile-time vs runtime
see Linus' reply to my first attempt[2].

Thanks,
Niklas

[0] https://lore.kernel.org/all/20230522105049.1467313-1-schnelle@linux.ibm.com/
[1] https://git.kernel.org/pub/scm/linux/kernel/git/niks/linux.git
[2] https://lore.kernel.org/lkml/CAHk-=wg80je=K7madF4e7WrRNp37e3qh6y10Svhdc7O8SZ_-8g@mail.gmail.com/

Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
---
Changes in v8:
- Don't remove "depends on !S390" for SERIAL_8250
- Link to v7: https://lore.kernel.org/r/20241008-b4-has_ioport-v7-0-8624c09a4d77@linux.ibm.com

Changes in v7:
- Renamed serial_8250_need_ioport() helper to
  serial_8250_warn_need_ioport() and move it to 8250_pcilib.c so it can
  be used in serial8250_pci_setup_port()
- Flattened if in serial8250_pci_setup_port() (Maciej)
- Removed gratuituous changes (Maciej)
- Removed is_upf_fourport() helper in favor of zeroing UPF_FOURPORT
  if CONFIG_HAS_IOPORT is not set (Maciej)
- Link to v6: https://lore.kernel.org/r/20241007-b4-has_ioport-v6-0-03f7240da6e5@linux.ibm.com

Changes since v5 / per subsystem patches:

drm:
- Add HAS_IOPORT dependency for GMA500
tty: serial:
- Make 8250 PCI driver emit an error message when trying to use devices
  which require I/O ports without CONFIG_HAS_IOPORT (Maciej)
- Use early returns + dead code elimination to skip inb()/outb() uses
  in quirks (Arnd)
- In 8250 PCI driver also handle fintek and moxi quirks
- In 8250 ports code handle um's defined(__i385__) &&
  defined(CONFIG_HAS_IOPORT) case
- Use IS_ENABLED() early return also in is_upf_fourport()
  __always_inline to force constant folding

---
Niklas Schnelle (5):
      hexagon: Don't select GENERIC_IOMAP without HAS_IOPORT support
      Bluetooth: add HAS_IOPORT dependencies
      drm: handle HAS_IOPORT dependencies
      tty: serial: handle HAS_IOPORT dependencies
      asm-generic/io.h: Remove I/O port accessors for HAS_IOPORT=n

 arch/hexagon/Kconfig                  |  1 -
 drivers/bluetooth/Kconfig             |  6 ++--
 drivers/gpu/drm/gma500/Kconfig        |  2 +-
 drivers/gpu/drm/qxl/Kconfig           |  1 +
 drivers/gpu/drm/tiny/bochs.c          | 17 ++++++++++
 drivers/gpu/drm/tiny/cirrus.c         |  2 ++
 drivers/gpu/drm/xe/Kconfig            |  2 +-
 drivers/tty/Kconfig                   |  4 +--
 drivers/tty/serial/8250/8250_early.c  |  4 +++
 drivers/tty/serial/8250/8250_pci.c    | 40 +++++++++++++++++++++++
 drivers/tty/serial/8250/8250_pcilib.c | 12 ++++++-
 drivers/tty/serial/8250/8250_pcilib.h |  2 ++
 drivers/tty/serial/8250/8250_port.c   | 27 +++++++++++++---
 drivers/tty/serial/8250/Kconfig       |  4 +--
 drivers/tty/serial/Kconfig            |  2 +-
 include/asm-generic/io.h              | 60 +++++++++++++++++++++++++++++++++++
 include/linux/serial_core.h           |  4 +++
 17 files changed, 174 insertions(+), 16 deletions(-)
---
base-commit: 8cf0b93919e13d1e8d4466eb4080a4c4d9d66d7b
change-id: 20241004-b4-has_ioport-60ac6ce1deb6

Best regards,
-- 
Niklas Schnelle

[PATCH v8 1/5] hexagon: Don't select GENERIC_IOMAP without HAS_IOPORT support

[Niklas Schnelle]

In a future patch HAS_IOPORT=n will disable inb()/outb() and friends at
compile time. As hexagon does not support I/O port access it also
the GENERIC_IOMAP mechanism of dynamically choosing between I/O port and
MMIO access doesn't work so don't select it.

Reviewed-by: Brian Cain <bcain@quicinc.com>
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>
---
 arch/hexagon/Kconfig | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig
index e233b5efa2761e35c416cbc147f6b6422a7c5b8f..5ea1bf4b7d4f5471a9c39ee9fb5c701455d21342 100644
--- a/arch/hexagon/Kconfig
+++ b/arch/hexagon/Kconfig
@@ -31,7 +31,6 @@ config HEXAGON
 	select HAVE_ARCH_TRACEHOOK
 	select NEED_SG_DMA_LENGTH
 	select NO_IOPORT_MAP
-	select GENERIC_IOMAP
 	select GENERIC_IOREMAP
 	select GENERIC_SMP_IDLE_THREAD
 	select STACKTRACE_SUPPORT

-- 
2.43.0

[PATCH v8 2/5] Bluetooth: add HAS_IOPORT dependencies

[Niklas Schnelle]

In a future patch HAS_IOPORT=n will disable inb()/outb() and friends at
compile time. We thus need to add HAS_IOPORT as dependency for those
drivers using them.

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>
---
 drivers/bluetooth/Kconfig | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/bluetooth/Kconfig b/drivers/bluetooth/Kconfig
index 18767b54df352e929692850dc789d9377839e094..4ab32abf0f48644715d4c27ec0d2fdaccef62b76 100644
--- a/drivers/bluetooth/Kconfig
+++ b/drivers/bluetooth/Kconfig
@@ -336,7 +336,7 @@ config BT_HCIBFUSB
 
 config BT_HCIDTL1
 	tristate "HCI DTL1 (PC Card) driver"
-	depends on PCMCIA
+	depends on PCMCIA && HAS_IOPORT
 	help
 	  Bluetooth HCI DTL1 (PC Card) driver.
 	  This driver provides support for Bluetooth PCMCIA devices with
@@ -349,7 +349,7 @@ config BT_HCIDTL1
 
 config BT_HCIBT3C
 	tristate "HCI BT3C (PC Card) driver"
-	depends on PCMCIA
+	depends on PCMCIA && HAS_IOPORT
 	select FW_LOADER
 	help
 	  Bluetooth HCI BT3C (PC Card) driver.
@@ -363,7 +363,7 @@ config BT_HCIBT3C
 
 config BT_HCIBLUECARD
 	tristate "HCI BlueCard (PC Card) driver"
-	depends on PCMCIA
+	depends on PCMCIA && HAS_IOPORT
 	help
 	  Bluetooth HCI BlueCard (PC Card) driver.
 	  This driver provides support for Bluetooth PCMCIA devices with

-- 
2.43.0

[PATCH v8 3/5] drm: handle HAS_IOPORT dependencies

[Niklas Schnelle]

In a future patch HAS_IOPORT=n will disable inb()/outb() and friends at
compile time. We thus need to add HAS_IOPORT as dependency for those
drivers using them. In the bochs driver there is optional MMIO support
detected at runtime, warn if this isn't taken when HAS_IOPORT is not
defined.

There is also a direct and hard coded use in cirrus.c which according to
the comment is only necessary during resume.  Let's just skip this as
for example s390 which doesn't have I/O port support also doesen't
support suspend/resume.

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>
---
 drivers/gpu/drm/gma500/Kconfig |  2 +-
 drivers/gpu/drm/qxl/Kconfig    |  1 +
 drivers/gpu/drm/tiny/bochs.c   | 17 +++++++++++++++++
 drivers/gpu/drm/tiny/cirrus.c  |  2 ++
 drivers/gpu/drm/xe/Kconfig     |  2 +-
 5 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/gma500/Kconfig b/drivers/gpu/drm/gma500/Kconfig
index efb4a2dd2f80885cb59c925d09401002278d7d61..23b7c14de5e29238ece939d5822d8a9ffc4675cc 100644
--- a/drivers/gpu/drm/gma500/Kconfig
+++ b/drivers/gpu/drm/gma500/Kconfig
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
 config DRM_GMA500
 	tristate "Intel GMA500/600/3600/3650 KMS Framebuffer"
-	depends on DRM && PCI && X86 && MMU
+	depends on DRM && PCI && X86 && MMU && HAS_IOPORT
 	select DRM_KMS_HELPER
 	select FB_IOMEM_HELPERS if DRM_FBDEV_EMULATION
 	select I2C
diff --git a/drivers/gpu/drm/qxl/Kconfig b/drivers/gpu/drm/qxl/Kconfig
index ca3f51c2a8fe1a383f8a2479f04b5c0b3fb14e44..d0e0d440c8d96564cb7b8ffd2385c44fc43f873d 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
 	select DRM_KMS_HELPER
 	select DRM_TTM
 	select DRM_TTM_HELPER
diff --git a/drivers/gpu/drm/tiny/bochs.c b/drivers/gpu/drm/tiny/bochs.c
index 31fc5d839e106ea4d5c8fe42d1bfc3c70291e3fb..0ed78d3d5774778f91de972ac27056938036e722 100644
--- a/drivers/gpu/drm/tiny/bochs.c
+++ b/drivers/gpu/drm/tiny/bochs.c
@@ -2,6 +2,7 @@
 
 #include <linux/module.h>
 #include <linux/pci.h>
+#include <linux/bug.h>
 
 #include <drm/drm_aperture.h>
 #include <drm/drm_atomic_helper.h>
@@ -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
 	}
 }
 
@@ -119,7 +122,11 @@ static u8 bochs_vga_readb(struct bochs_device *bochs, u16 ioport)
 
 		return readb(bochs->mmio + offset);
 	} else {
+#ifdef CONFIG_HAS_IOPORT
 		return inb(ioport);
+#else
+		return 0xff;
+#endif
 	}
 }
 
@@ -132,8 +139,12 @@ static u16 bochs_dispi_read(struct bochs_device *bochs, u16 reg)
 
 		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;
 }
@@ -145,8 +156,10 @@ static void bochs_dispi_write(struct bochs_device *bochs, u16 reg, u16 val)
 
 		writew(val, bochs->mmio + offset);
 	} else {
+#ifdef CONFIG_HAS_IOPORT
 		outw(reg, VBE_DISPI_IOPORT_INDEX);
 		outw(val, VBE_DISPI_IOPORT_DATA);
+#endif
 	}
 }
 
@@ -229,6 +242,10 @@ static int bochs_hw_init(struct drm_device *dev)
 			return -ENOMEM;
 		}
 	} else {
+		if (!IS_ENABLED(CONFIG_HAS_IOPORT)) {
+			DRM_ERROR("I/O ports are not supported\n");
+			return -EIO;
+		}
 		ioaddr = VBE_DISPI_IOPORT_INDEX;
 		iosize = 2;
 		if (!request_region(ioaddr, iosize, "bochs-drm")) {
diff --git a/drivers/gpu/drm/tiny/cirrus.c b/drivers/gpu/drm/tiny/cirrus.c
index 751326e3d9c374baf72115492aeefff2b73869f0..e31e1df029ab0272c4a1ff0ab3eb026ca679b560 100644
--- a/drivers/gpu/drm/tiny/cirrus.c
+++ b/drivers/gpu/drm/tiny/cirrus.c
@@ -509,8 +509,10 @@ static void cirrus_crtc_helper_atomic_enable(struct drm_crtc *crtc,
 
 	cirrus_mode_set(cirrus, &crtc_state->mode);
 
+#ifdef CONFIG_HAS_IOPORT
 	/* Unblank (needed on S3 resume, vgabios doesn't do it then) */
 	outb(VGA_AR_ENABLE_DISPLAY, VGA_ATT_W);
+#endif
 
 	drm_dev_exit(idx);
 }
diff --git a/drivers/gpu/drm/xe/Kconfig b/drivers/gpu/drm/xe/Kconfig
index 7bbe46a98ff1f449bc2af30686585a00e9e8af93..116f58774135fc3a9f37d6d72d41340f5c812297 100644
--- a/drivers/gpu/drm/xe/Kconfig
+++ b/drivers/gpu/drm/xe/Kconfig
@@ -49,7 +49,7 @@ config DRM_XE
 
 config DRM_XE_DISPLAY
 	bool "Enable display support"
-	depends on DRM_XE && DRM_XE=m
+	depends on DRM_XE && DRM_XE=m && HAS_IOPORT
 	select FB_IOMEM_HELPERS
 	select I2C
 	select I2C_ALGOBIT

-- 
2.43.0

[PATCH v8 4/5] tty: serial: handle HAS_IOPORT dependencies

[Niklas Schnelle]

In a future patch HAS_IOPORT=n will disable inb()/outb() and friends at
compile time. We thus need to add HAS_IOPORT as dependency for those
drivers using them unconditionally. Some 8250 serial drivers support
MMIO only use, so fence only the parts requiring I/O ports and print an
error message if a device can't be supported with the current
configuration.

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>
---
 drivers/tty/Kconfig                   |  4 ++--
 drivers/tty/serial/8250/8250_early.c  |  4 ++++
 drivers/tty/serial/8250/8250_pci.c    | 40 +++++++++++++++++++++++++++++++++++
 drivers/tty/serial/8250/8250_pcilib.c | 12 ++++++++++-
 drivers/tty/serial/8250/8250_pcilib.h |  2 ++
 drivers/tty/serial/8250/8250_port.c   | 27 +++++++++++++++++++----
 drivers/tty/serial/8250/Kconfig       |  4 ++--
 drivers/tty/serial/Kconfig            |  2 +-
 include/linux/serial_core.h           |  4 ++++
 9 files changed, 89 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index a45d423ad10f02c3a818021bbb18655a8b690500..63a494d36a1fdceba5a7b39f4516060e48af0cc6 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -220,7 +220,7 @@ config MOXA_INTELLIO
 
 config MOXA_SMARTIO
 	tristate "Moxa SmartIO support v. 2.0"
-	depends on SERIAL_NONSTANDARD && PCI
+	depends on SERIAL_NONSTANDARD && PCI && HAS_IOPORT
 	help
 	  Say Y here if you have a Moxa SmartIO multiport serial card and/or
 	  want to help develop a new version of this driver.
@@ -302,7 +302,7 @@ config GOLDFISH_TTY_EARLY_CONSOLE
 
 config IPWIRELESS
 	tristate "IPWireless 3G UMTS PCMCIA card support"
-	depends on PCMCIA && NETDEVICES
+	depends on PCMCIA && NETDEVICES && HAS_IOPORT
 	select PPP
 	help
 	  This is a driver for 3G UMTS PCMCIA card from IPWireless company. In
diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
index 6176083d0341ca10edebe5c4eebfffc922a61472..84242292176570cd2c92afbd4755d303827a4abc 100644
--- a/drivers/tty/serial/8250/8250_early.c
+++ b/drivers/tty/serial/8250/8250_early.c
@@ -46,8 +46,10 @@ static unsigned int serial8250_early_in(struct uart_port *port, int offset)
 		return readl(port->membase + offset);
 	case UPIO_MEM32BE:
 		return ioread32be(port->membase + offset);
+#ifdef CONFIG_HAS_IOPORT
 	case UPIO_PORT:
 		return inb(port->iobase + offset);
+#endif
 	default:
 		return 0;
 	}
@@ -70,9 +72,11 @@ static void serial8250_early_out(struct uart_port *port, int offset, int value)
 	case UPIO_MEM32BE:
 		iowrite32be(value, port->membase + offset);
 		break;
+#ifdef CONFIG_HAS_IOPORT
 	case UPIO_PORT:
 		outb(value, port->iobase + offset);
 		break;
+#endif
 	}
 }
 
diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index 6709b6a5f3011db38acc58dc7223158fe4fcf72e..7d7a6d62c09ceabcf4094d539c565ed09c153561 100644
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -964,6 +964,9 @@ static int pci_ite887x_init(struct pci_dev *dev)
 	struct resource *iobase = NULL;
 	u32 miscr, uartbar, ioport;
 
+	if (!IS_ENABLED(CONFIG_HAS_IOPORT))
+		return serial_8250_warn_need_ioport(dev);
+
 	/* search for the base-ioport */
 	for (i = 0; i < ARRAY_SIZE(inta_addr); i++) {
 		iobase = request_region(inta_addr[i], ITE_887x_IOSIZE,
@@ -1514,6 +1517,9 @@ static int pci_quatech_init(struct pci_dev *dev)
 	const struct pci_device_id *match;
 	bool amcc = false;
 
+	if (!IS_ENABLED(CONFIG_HAS_IOPORT))
+		return serial_8250_warn_need_ioport(dev);
+
 	match = pci_match_id(quatech_cards, dev);
 	if (match)
 		amcc = match->driver_data;
@@ -1538,6 +1544,9 @@ static int pci_quatech_setup(struct serial_private *priv,
 		  const struct pciserial_board *board,
 		  struct uart_8250_port *port, int idx)
 {
+	if (!IS_ENABLED(CONFIG_HAS_IOPORT))
+		return serial_8250_warn_need_ioport(priv->dev);
+
 	/* Needed by pci_quatech calls below */
 	port->port.iobase = pci_resource_start(priv->dev, FL_GET_BASE(board->flags));
 	/* Set up the clocking */
@@ -1655,6 +1664,9 @@ static int pci_fintek_setup(struct serial_private *priv,
 	u8 config_base;
 	u16 iobase;
 
+	if (!IS_ENABLED(CONFIG_HAS_IOPORT))
+		return serial_8250_warn_need_ioport(pdev);
+
 	config_base = 0x40 + 0x08 * idx;
 
 	/* Get the io address from configuration space */
@@ -1686,6 +1698,9 @@ static int pci_fintek_init(struct pci_dev *dev)
 	u8 config_base;
 	struct serial_private *priv = pci_get_drvdata(dev);
 
+	if (!IS_ENABLED(CONFIG_HAS_IOPORT))
+		return serial_8250_warn_need_ioport(dev);
+
 	if (!(pci_resource_flags(dev, 5) & IORESOURCE_IO) ||
 			!(pci_resource_flags(dev, 4) & IORESOURCE_IO) ||
 			!(pci_resource_flags(dev, 3) & IORESOURCE_IO))
@@ -1864,6 +1879,9 @@ static int kt_serial_setup(struct serial_private *priv,
 			   const struct pciserial_board *board,
 			   struct uart_8250_port *port, int idx)
 {
+	if (!IS_ENABLED(CONFIG_HAS_IOPORT))
+		return serial_8250_warn_need_ioport(priv->dev);
+
 	port->port.flags |= UPF_BUG_THRE;
 	port->port.serial_in = kt_serial_in;
 	port->port.handle_break = kt_handle_break;
@@ -1884,6 +1902,9 @@ pci_wch_ch353_setup(struct serial_private *priv,
 		    const struct pciserial_board *board,
 		    struct uart_8250_port *port, int idx)
 {
+	if (!IS_ENABLED(CONFIG_HAS_IOPORT))
+		return serial_8250_warn_need_ioport(priv->dev);
+
 	port->port.flags |= UPF_FIXED_TYPE;
 	port->port.type = PORT_16550A;
 	return pci_default_setup(priv, board, port, idx);
@@ -1894,6 +1915,9 @@ pci_wch_ch355_setup(struct serial_private *priv,
 		const struct pciserial_board *board,
 		struct uart_8250_port *port, int idx)
 {
+	if (!IS_ENABLED(CONFIG_HAS_IOPORT))
+		return serial_8250_warn_need_ioport(priv->dev);
+
 	port->port.flags |= UPF_FIXED_TYPE;
 	port->port.type = PORT_16550A;
 	return pci_default_setup(priv, board, port, idx);
@@ -1904,6 +1928,9 @@ pci_wch_ch38x_setup(struct serial_private *priv,
 		    const struct pciserial_board *board,
 		    struct uart_8250_port *port, int idx)
 {
+	if (!IS_ENABLED(CONFIG_HAS_IOPORT))
+		return serial_8250_warn_need_ioport(priv->dev);
+
 	port->port.flags |= UPF_FIXED_TYPE;
 	port->port.type = PORT_16850;
 	return pci_default_setup(priv, board, port, idx);
@@ -1918,6 +1945,8 @@ static int pci_wch_ch38x_init(struct pci_dev *dev)
 	int max_port;
 	unsigned long iobase;
 
+	if (!IS_ENABLED(CONFIG_HAS_IOPORT))
+		return serial_8250_warn_need_ioport(dev);
 
 	switch (dev->device) {
 	case 0x3853: /* 8 ports */
@@ -1937,6 +1966,11 @@ static void pci_wch_ch38x_exit(struct pci_dev *dev)
 {
 	unsigned long iobase;
 
+	if (!IS_ENABLED(CONFIG_HAS_IOPORT)) {
+		serial_8250_warn_need_ioport(dev);
+		return;
+	}
+
 	iobase = pci_resource_start(dev, 0);
 	outb(0x0, iobase + CH384_XINT_ENABLE_REG);
 }
@@ -2052,6 +2086,9 @@ static int pci_moxa_init(struct pci_dev *dev)
 	unsigned int i, num_ports = moxa_get_nports(device);
 	u8 val, init_mode = MOXA_RS232;
 
+	if (!IS_ENABLED(CONFIG_HAS_IOPORT))
+		return serial_8250_warn_need_ioport(dev);
+
 	if (!(pci_moxa_supported_rs(dev) & MOXA_SUPP_RS232)) {
 		init_mode = MOXA_RS422;
 	}
@@ -2084,6 +2121,9 @@ pci_moxa_setup(struct serial_private *priv,
 	unsigned int bar = FL_GET_BASE(board->flags);
 	int offset;
 
+	if (!IS_ENABLED(CONFIG_HAS_IOPORT))
+		return serial_8250_warn_need_ioport(priv->dev);
+
 	if (board->num_ports == 4 && idx == 3)
 		offset = 7 * board->uart_offset;
 	else
diff --git a/drivers/tty/serial/8250/8250_pcilib.c b/drivers/tty/serial/8250/8250_pcilib.c
index ea906d721b2c3eac15c9e8d62cc6fa56c3ef6150..ec4d041778027a0c9f27facbb97c2b74819cfda3 100644
--- a/drivers/tty/serial/8250/8250_pcilib.c
+++ b/drivers/tty/serial/8250/8250_pcilib.c
@@ -12,6 +12,14 @@
 #include "8250.h"
 #include "8250_pcilib.h"
 
+int serial_8250_warn_need_ioport(struct pci_dev *dev)
+{
+	dev_warn(&dev->dev,
+		 "Serial port not supported because of missing I/O resource\n");
+
+	return -ENXIO;
+}
+
 int serial8250_pci_setup_port(struct pci_dev *dev, struct uart_8250_port *port,
 		   u8 bar, unsigned int offset, int regshift)
 {
@@ -27,12 +35,14 @@ int serial8250_pci_setup_port(struct pci_dev *dev, struct uart_8250_port *port,
 		port->port.mapbase = pci_resource_start(dev, bar) + offset;
 		port->port.membase = pcim_iomap_table(dev)[bar] + offset;
 		port->port.regshift = regshift;
-	} else {
+	} else if (IS_ENABLED(CONFIG_HAS_IOPORT)) {
 		port->port.iotype = UPIO_PORT;
 		port->port.iobase = pci_resource_start(dev, bar) + offset;
 		port->port.mapbase = 0;
 		port->port.membase = NULL;
 		port->port.regshift = 0;
+	} else {
+		return serial_8250_warn_need_ioport(dev);
 	}
 	return 0;
 }
diff --git a/drivers/tty/serial/8250/8250_pcilib.h b/drivers/tty/serial/8250/8250_pcilib.h
index 1aaf1b50ce9cc9d78c098e0495838c17eb8752cd..16a274574cdef938fe7700d30b19e75dbbd9b748 100644
--- a/drivers/tty/serial/8250/8250_pcilib.h
+++ b/drivers/tty/serial/8250/8250_pcilib.h
@@ -13,3 +13,5 @@ struct uart_8250_port;
 
 int serial8250_pci_setup_port(struct pci_dev *dev, struct uart_8250_port *port, u8 bar,
 		   unsigned int offset, int regshift);
+
+int serial_8250_warn_need_ioport(struct pci_dev *dev);
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 3509af7dc52b8816f2f5ab58f0d999696f7483e7..91369f542b0bc7fc1d044f24db9a4ac98b394660 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -338,6 +338,7 @@ static void default_serial_dl_write(struct uart_8250_port *up, u32 value)
 	serial_out(up, UART_DLM, value >> 8 & 0xff);
 }
 
+#ifdef CONFIG_HAS_IOPORT
 static unsigned int hub6_serial_in(struct uart_port *p, int offset)
 {
 	offset = offset << p->regshift;
@@ -351,6 +352,7 @@ static void hub6_serial_out(struct uart_port *p, int offset, int value)
 	outb(p->hub6 - 1 + offset, p->iobase);
 	outb(value, p->iobase + 1);
 }
+#endif /* CONFIG_HAS_IOPORT */
 
 static unsigned int mem_serial_in(struct uart_port *p, int offset)
 {
@@ -400,6 +402,7 @@ static unsigned int mem32be_serial_in(struct uart_port *p, int offset)
 	return ioread32be(p->membase + offset);
 }
 
+#ifdef CONFIG_HAS_IOPORT
 static unsigned int io_serial_in(struct uart_port *p, int offset)
 {
 	offset = offset << p->regshift;
@@ -411,6 +414,15 @@ static void io_serial_out(struct uart_port *p, int offset, int value)
 	offset = offset << p->regshift;
 	outb(value, p->iobase + offset);
 }
+#endif
+static unsigned int no_serial_in(struct uart_port *p, int offset)
+{
+	return (unsigned int)-1;
+}
+
+static void no_serial_out(struct uart_port *p, int offset, int value)
+{
+}
 
 static int serial8250_default_handle_irq(struct uart_port *port);
 
@@ -422,10 +434,12 @@ static void set_io_from_upio(struct uart_port *p)
 	up->dl_write = default_serial_dl_write;
 
 	switch (p->iotype) {
+#ifdef CONFIG_HAS_IOPORT
 	case UPIO_HUB6:
 		p->serial_in = hub6_serial_in;
 		p->serial_out = hub6_serial_out;
 		break;
+#endif
 
 	case UPIO_MEM:
 		p->serial_in = mem_serial_in;
@@ -446,11 +460,16 @@ static void set_io_from_upio(struct uart_port *p)
 		p->serial_in = mem32be_serial_in;
 		p->serial_out = mem32be_serial_out;
 		break;
-
-	default:
+#ifdef CONFIG_HAS_IOPORT
+	case UPIO_PORT:
 		p->serial_in = io_serial_in;
 		p->serial_out = io_serial_out;
 		break;
+#endif
+	default:
+		WARN(1, "Unsupported UART type %x\n", p->iotype);
+		p->serial_in = no_serial_in;
+		p->serial_out = no_serial_out;
 	}
 	/* Remember loaded iotype */
 	up->cur_iotype = p->iotype;
@@ -1174,7 +1193,7 @@ static void autoconfig(struct uart_8250_port *up)
 		 */
 		scratch = serial_in(up, UART_IER);
 		serial_out(up, UART_IER, 0);
-#ifdef __i386__
+#if defined(__i386__) && defined(CONFIG_HAS_IOPORT)
 		outb(0xff, 0x080);
 #endif
 		/*
@@ -1183,7 +1202,7 @@ static void autoconfig(struct uart_8250_port *up)
 		 */
 		scratch2 = serial_in(up, UART_IER) & UART_IER_ALL_INTR;
 		serial_out(up, UART_IER, UART_IER_ALL_INTR);
-#ifdef __i386__
+#if defined(__i386__) && defined(CONFIG_HAS_IOPORT)
 		outb(0, 0x080);
 #endif
 		scratch3 = serial_in(up, UART_IER) & UART_IER_ALL_INTR;
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 47ff50763c048c89b19b7c9f13f462bc5368ab43..1eb20350fcf432d41cb416bed3be72ed8ab129bb 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -72,7 +72,7 @@ config SERIAL_8250_16550A_VARIANTS
 
 config SERIAL_8250_FINTEK
 	bool "Support for Fintek variants"
-	depends on SERIAL_8250
+	depends on SERIAL_8250 && HAS_IOPORT
 	help
 	  Selecting this option will add support for the RS232 and RS485
 	  capabilities of the Fintek F81216A LPC to 4 UART as well similar
@@ -163,7 +163,7 @@ config SERIAL_8250_HP300
 
 config SERIAL_8250_CS
 	tristate "8250/16550 PCMCIA device support"
-	depends on PCMCIA && SERIAL_8250
+	depends on PCMCIA && SERIAL_8250 && HAS_IOPORT
 	help
 	  Say Y here to enable support for 16-bit PCMCIA serial devices,
 	  including serial port cards, modems, and the modem functions of
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 28e4beeabf8f373fc76e09ea7d1c9d55a66f4964..45f0f779fbf960e9fa66375dbc44c379edc63bef 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -877,7 +877,7 @@ config SERIAL_TXX9_STDSERIAL
 
 config SERIAL_JSM
 	tristate "Digi International NEO and Classic PCI Support"
-	depends on PCI
+	depends on PCI && HAS_IOPORT
 	select SERIAL_CORE
 	help
 	  This is a driver for Digi International's Neo and Classic series
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 4ab65874a850b4402ca3a7d3bdda597d7d5093f9..743b4afaad4c89a6028e592be2cae2643614c89b 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -505,7 +505,11 @@ struct uart_port {
 	 * The remaining bits are serial-core specific and not modifiable by
 	 * userspace.
 	 */
+#ifdef CONFIG_HAS_IOPORT
 #define UPF_FOURPORT		((__force upf_t) ASYNC_FOURPORT       /* 1  */ )
+#else
+#define UPF_FOURPORT		0
+#endif
 #define UPF_SAK			((__force upf_t) ASYNC_SAK            /* 2  */ )
 #define UPF_SPD_HI		((__force upf_t) ASYNC_SPD_HI         /* 4  */ )
 #define UPF_SPD_VHI		((__force upf_t) ASYNC_SPD_VHI        /* 5  */ )

-- 
2.43.0

[PATCH v8 5/5] asm-generic/io.h: Remove I/O port accessors for HAS_IOPORT=n

[Niklas Schnelle]

With all subsystems and drivers either declaring their dependence on
HAS_IOPORT or fencing I/O port specific code sections we can finally
make inb()/outb() and friends compile-time dependent on HAS_IOPORT as
suggested by Linus in the linked mail. The main benefit of this is that
on platforms such as s390 which have no meaningful way of implementing
inb()/outb() their use without the proper HAS_IOPORT dependency will
result in easy to catch and fix compile-time errors instead of compiling
code that can never work.

Link: https://lore.kernel.org/lkml/CAHk-=wg80je=K7madF4e7WrRNp37e3qh6y10Svhdc7O8SZ_-8g@mail.gmail.com/
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>
---
 include/asm-generic/io.h | 60 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index 80de699bf6af4b7b77f582c0469c43e978f67a43..1027be6a62bcbcd5f6797e0fa42035208d0ca79f 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -540,6 +540,7 @@ static inline void writesq(volatile void __iomem *addr, const void *buffer,
 
 #if !defined(inb) && !defined(_inb)
 #define _inb _inb
+#ifdef CONFIG_HAS_IOPORT
 static inline u8 _inb(unsigned long addr)
 {
 	u8 val;
@@ -549,10 +550,15 @@ static inline u8 _inb(unsigned long addr)
 	__io_par(val);
 	return val;
 }
+#else
+u8 _inb(unsigned long addr)
+	__compiletime_error("inb()) requires CONFIG_HAS_IOPORT");
+#endif
 #endif
 
 #if !defined(inw) && !defined(_inw)
 #define _inw _inw
+#ifdef CONFIG_HAS_IOPORT
 static inline u16 _inw(unsigned long addr)
 {
 	u16 val;
@@ -562,10 +568,15 @@ static inline u16 _inw(unsigned long addr)
 	__io_par(val);
 	return val;
 }
+#else
+u16 _inw(unsigned long addr)
+	__compiletime_error("inw() requires CONFIG_HAS_IOPORT");
+#endif
 #endif
 
 #if !defined(inl) && !defined(_inl)
 #define _inl _inl
+#ifdef CONFIG_HAS_IOPORT
 static inline u32 _inl(unsigned long addr)
 {
 	u32 val;
@@ -575,36 +586,55 @@ static inline u32 _inl(unsigned long addr)
 	__io_par(val);
 	return val;
 }
+#else
+u32 _inl(unsigned long addr)
+	__compiletime_error("inl() requires CONFIG_HAS_IOPORT");
+#endif
 #endif
 
 #if !defined(outb) && !defined(_outb)
 #define _outb _outb
+#ifdef CONFIG_HAS_IOPORT
 static inline void _outb(u8 value, unsigned long addr)
 {
 	__io_pbw();
 	__raw_writeb(value, PCI_IOBASE + addr);
 	__io_paw();
 }
+#else
+void _outb(u8 value, unsigned long addr)
+	__compiletime_error("outb() requires CONFIG_HAS_IOPORT");
+#endif
 #endif
 
 #if !defined(outw) && !defined(_outw)
 #define _outw _outw
+#ifdef CONFIG_HAS_IOPORT
 static inline void _outw(u16 value, unsigned long addr)
 {
 	__io_pbw();
 	__raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
 	__io_paw();
 }
+#else
+void _outw(u16 value, unsigned long addr)
+	__compiletime_error("outw() requires CONFIG_HAS_IOPORT");
+#endif
 #endif
 
 #if !defined(outl) && !defined(_outl)
 #define _outl _outl
+#ifdef CONFIG_HAS_IOPORT
 static inline void _outl(u32 value, unsigned long addr)
 {
 	__io_pbw();
 	__raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
 	__io_paw();
 }
+#else
+void _outl(u32 value, unsigned long addr)
+	__compiletime_error("outl() requires CONFIG_HAS_IOPORT");
+#endif
 #endif
 
 #include <linux/logic_pio.h>
@@ -688,53 +718,83 @@ static inline void outl_p(u32 value, unsigned long addr)
 
 #ifndef insb
 #define insb insb
+#ifdef CONFIG_HAS_IOPORT
 static inline void insb(unsigned long addr, void *buffer, unsigned int count)
 {
 	readsb(PCI_IOBASE + addr, buffer, count);
 }
+#else
+void insb(unsigned long addr, void *buffer, unsigned int count)
+	__compiletime_error("insb() requires HAS_IOPORT");
+#endif
 #endif
 
 #ifndef insw
 #define insw insw
+#ifdef CONFIG_HAS_IOPORT
 static inline void insw(unsigned long addr, void *buffer, unsigned int count)
 {
 	readsw(PCI_IOBASE + addr, buffer, count);
 }
+#else
+void insw(unsigned long addr, void *buffer, unsigned int count)
+	__compiletime_error("insw() requires HAS_IOPORT");
+#endif
 #endif
 
 #ifndef insl
 #define insl insl
+#ifdef CONFIG_HAS_IOPORT
 static inline void insl(unsigned long addr, void *buffer, unsigned int count)
 {
 	readsl(PCI_IOBASE + addr, buffer, count);
 }
+#else
+void insl(unsigned long addr, void *buffer, unsigned int count)
+	__compiletime_error("insl() requires HAS_IOPORT");
+#endif
 #endif
 
 #ifndef outsb
 #define outsb outsb
+#ifdef CONFIG_HAS_IOPORT
 static inline void outsb(unsigned long addr, const void *buffer,
 			 unsigned int count)
 {
 	writesb(PCI_IOBASE + addr, buffer, count);
 }
+#else
+void outsb(unsigned long addr, const void *buffer, unsigned int count)
+	__compiletime_error("outsb() requires HAS_IOPORT");
+#endif
 #endif
 
 #ifndef outsw
 #define outsw outsw
+#ifdef CONFIG_HAS_IOPORT
 static inline void outsw(unsigned long addr, const void *buffer,
 			 unsigned int count)
 {
 	writesw(PCI_IOBASE + addr, buffer, count);
 }
+#else
+void outsw(unsigned long addr, const void *buffer, unsigned int count)
+	__compiletime_error("outsw() requires HAS_IOPORT");
+#endif
 #endif
 
 #ifndef outsl
 #define outsl outsl
+#ifdef CONFIG_HAS_IOPORT
 static inline void outsl(unsigned long addr, const void *buffer,
 			 unsigned int count)
 {
 	writesl(PCI_IOBASE + addr, buffer, count);
 }
+#else
+void outsl(unsigned long addr, const void *buffer, unsigned int count)
+	__compiletime_error("outsl() requires HAS_IOPORT");
+#endif
 #endif
 
 #ifndef insb_p

-- 
2.43.0

Re: [PATCH v8 4/5] tty: serial: handle HAS_IOPORT dependencies

[Greg Kroah-Hartman]

On Tue, Oct 08, 2024 at 02:39:45PM +0200, Niklas Schnelle wrote:
> In a future patch HAS_IOPORT=n will disable inb()/outb() and friends at
> compile time. We thus need to add HAS_IOPORT as dependency for those
> drivers using them unconditionally. Some 8250 serial drivers support
> MMIO only use, so fence only the parts requiring I/O ports and print an
> error message if a device can't be supported with the current
> configuration.
> 
> 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>
> ---

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Re: [PATCH v8 4/5] tty: serial: handle HAS_IOPORT dependencies

[Maciej W. Rozycki]

On Tue, 8 Oct 2024, Niklas Schnelle wrote:

> In a future patch HAS_IOPORT=n will disable inb()/outb() and friends at
> compile time. We thus need to add HAS_IOPORT as dependency for those
> drivers using them unconditionally. Some 8250 serial drivers support
> MMIO only use, so fence only the parts requiring I/O ports and print an
> error message if a device can't be supported with the current
> configuration.
> 
> 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>
> ---

Reviewed-by: Maciej W. Rozycki <macro@orcam.me.uk>

  Maciej

Re: [PATCH v8 3/5] drm: handle HAS_IOPORT dependencies

[Thomas Zimmermann]

Hi

Am 08.10.24 um 14:39 schrieb Niklas Schnelle:
> In a future patch HAS_IOPORT=n will disable inb()/outb() and friends at
> compile time. We thus need to add HAS_IOPORT as dependency for those
> drivers using them. In the bochs driver there is optional MMIO support
> detected at runtime, warn if this isn't taken when HAS_IOPORT is not
> defined.
>
> There is also a direct and hard coded use in cirrus.c which according to
> the comment is only necessary during resume.  Let's just skip this as
> for example s390 which doesn't have I/O port support also doesen't
> support suspend/resume.
>
> 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>

I feel like I reviewed this before, but can't find it.

> ---
>   drivers/gpu/drm/gma500/Kconfig |  2 +-
>   drivers/gpu/drm/qxl/Kconfig    |  1 +
>   drivers/gpu/drm/tiny/bochs.c   | 17 +++++++++++++++++
>   drivers/gpu/drm/tiny/cirrus.c  |  2 ++
>   drivers/gpu/drm/xe/Kconfig     |  2 +-
>   5 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/gma500/Kconfig b/drivers/gpu/drm/gma500/Kconfig
> index efb4a2dd2f80885cb59c925d09401002278d7d61..23b7c14de5e29238ece939d5822d8a9ffc4675cc 100644
> --- a/drivers/gpu/drm/gma500/Kconfig
> +++ b/drivers/gpu/drm/gma500/Kconfig
> @@ -1,7 +1,7 @@
>   # SPDX-License-Identifier: GPL-2.0-only
>   config DRM_GMA500
>   	tristate "Intel GMA500/600/3600/3650 KMS Framebuffer"
> -	depends on DRM && PCI && X86 && MMU
> +	depends on DRM && PCI && X86 && MMU && HAS_IOPORT
>   	select DRM_KMS_HELPER
>   	select FB_IOMEM_HELPERS if DRM_FBDEV_EMULATION
>   	select I2C
> diff --git a/drivers/gpu/drm/qxl/Kconfig b/drivers/gpu/drm/qxl/Kconfig
> index ca3f51c2a8fe1a383f8a2479f04b5c0b3fb14e44..d0e0d440c8d96564cb7b8ffd2385c44fc43f873d 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 (&& && &&)?

>   	select DRM_KMS_HELPER
>   	select DRM_TTM
>   	select DRM_TTM_HELPER
> diff --git a/drivers/gpu/drm/tiny/bochs.c b/drivers/gpu/drm/tiny/bochs.c
> index 31fc5d839e106ea4d5c8fe42d1bfc3c70291e3fb..0ed78d3d5774778f91de972ac27056938036e722 100644
> --- a/drivers/gpu/drm/tiny/bochs.c
> +++ b/drivers/gpu/drm/tiny/bochs.c
> @@ -2,6 +2,7 @@
>   
>   #include <linux/module.h>
>   #include <linux/pci.h>
> +#include <linux/bug.h>

Alphabetic sorting please.

>   
>   #include <drm/drm_aperture.h>
>   #include <drm/drm_atomic_helper.h>
> @@ -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?

>   	}
>   }
>   
> @@ -119,7 +122,11 @@ static u8 bochs_vga_readb(struct bochs_device *bochs, u16 ioport)
>   
>   		return readb(bochs->mmio + offset);
>   	} else {
> +#ifdef CONFIG_HAS_IOPORT
>   		return inb(ioport);
> +#else
> +		return 0xff;
> +#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?

>   	}
>   }
>   
> @@ -132,8 +139,12 @@ static u16 bochs_dispi_read(struct bochs_device *bochs, u16 reg)
>   
>   		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;
>   }
> @@ -145,8 +156,10 @@ static void bochs_dispi_write(struct bochs_device *bochs, u16 reg, u16 val)
>   
>   		writew(val, bochs->mmio + offset);
>   	} else {
> +#ifdef CONFIG_HAS_IOPORT
>   		outw(reg, VBE_DISPI_IOPORT_INDEX);
>   		outw(val, VBE_DISPI_IOPORT_DATA);
> +#endif
>   	}
>   }
>   
> @@ -229,6 +242,10 @@ static int bochs_hw_init(struct drm_device *dev)
>   			return -ENOMEM;
>   		}
>   	} else {
> +		if (!IS_ENABLED(CONFIG_HAS_IOPORT)) {
> +			DRM_ERROR("I/O ports are not supported\n");
> +			return -EIO;
> +		}

It would be nicer to use an "} else if(IOPORT) {" here and put the 
"return -EIO" into a trailing else branch.

If you want to add an error message, please don't use DRM_ERROR(). In 
this case, dev_err(dev->dev, "...\n") seems appropriate.

Best regards
Thomas

>   		ioaddr = VBE_DISPI_IOPORT_INDEX;
>   		iosize = 2;
>   		if (!request_region(ioaddr, iosize, "bochs-drm")) {
> diff --git a/drivers/gpu/drm/tiny/cirrus.c b/drivers/gpu/drm/tiny/cirrus.c
> index 751326e3d9c374baf72115492aeefff2b73869f0..e31e1df029ab0272c4a1ff0ab3eb026ca679b560 100644
> --- a/drivers/gpu/drm/tiny/cirrus.c
> +++ b/drivers/gpu/drm/tiny/cirrus.c
> @@ -509,8 +509,10 @@ static void cirrus_crtc_helper_atomic_enable(struct drm_crtc *crtc,
>   
>   	cirrus_mode_set(cirrus, &crtc_state->mode);
>   
> +#ifdef CONFIG_HAS_IOPORT
>   	/* Unblank (needed on S3 resume, vgabios doesn't do it then) */
>   	outb(VGA_AR_ENABLE_DISPLAY, VGA_ATT_W);
> +#endif
>   
>   	drm_dev_exit(idx);
>   }
> diff --git a/drivers/gpu/drm/xe/Kconfig b/drivers/gpu/drm/xe/Kconfig
> index 7bbe46a98ff1f449bc2af30686585a00e9e8af93..116f58774135fc3a9f37d6d72d41340f5c812297 100644
> --- a/drivers/gpu/drm/xe/Kconfig
> +++ b/drivers/gpu/drm/xe/Kconfig
> @@ -49,7 +49,7 @@ config DRM_XE
>   
>   config DRM_XE_DISPLAY
>   	bool "Enable display support"
> -	depends on DRM_XE && DRM_XE=m
> +	depends on DRM_XE && DRM_XE=m && HAS_IOPORT
>   	select FB_IOMEM_HELPERS
>   	select I2C
>   	select I2C_ALGOBIT
>

-- 
--
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)

Re: [PATCH v8 3/5] drm: handle HAS_IOPORT dependencies

[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
 	}
 }
 
@@ -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.

     Arnd

Re: [PATCH v8 3/5] drm: handle HAS_IOPORT dependencies

[Thomas Zimmermann]

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)

Re: [PATCH v8 3/5] drm: handle HAS_IOPORT dependencies

[Thomas Zimmermann]

>
> I'd review a separate series for such a change.

Could also be a single patch here, of course.



-- 
--
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)

Re: [PATCH v8 3/5] drm: handle HAS_IOPORT dependencies

[Niklas Schnelle]

On Mon, 2024-10-21 at 12:58 +0200, Thomas Zimmermann wrote:
> 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
>      }
> }
> 

I think if the helper were __always_inline we could still take
advantage of the dead code elimination and combine this with Arnd's
approach. Though I feel like it is a bit odd to try to do the MMIO
approach despite bochs->mmio being false on !HAS_IOPORT systems.
Is that what you wanted to correct by keeping the #ifdef
CONFIG_HAS_IOPORT around the else? And yes the warning makes sense to
me too.

Thanks,
Niklas

Re: [PATCH v8 3/5] drm: handle HAS_IOPORT dependencies

[Arnd Bergmann]

On Mon, Oct 21, 2024, at 10:58, Thomas Zimmermann wrote:
> Am 21.10.24 um 12:08 schrieb Arnd Bergmann:
>> On Mon, Oct 21, 2024, at 07:52, Thomas Zimmermann wrote:
>> --- 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) {

I meant IS_ENABLED() of course.

> 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
>      }

Yes, that helper function look fine, but it should then
be either __always_inline or a macro. With that, the
#ifdef is not needed since gcc only warns if there is
a path that leads to outb() actually getting called.

      Arnd

Re: [PATCH v8 3/5] drm: handle HAS_IOPORT dependencies

[Niklas Schnelle]

On Mon, Oct 21, 2024 at 01:18:20PM +0200, Niklas Schnelle wrote:
> On Mon, 2024-10-21 at 12:58 +0200, Thomas Zimmermann wrote:
> > 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
> >      }
> > }
> > 
> 
> I think if the helper were __always_inline we could still take
> advantage of the dead code elimination and combine this with Arnd's
> approach. Though I feel like it is a bit odd to try to do the MMIO
> approach despite bochs->mmio being false on !HAS_IOPORT systems.
> Is that what you wanted to correct by keeping the #ifdef
> CONFIG_HAS_IOPORT around the else? And yes the warning makes sense to
> me too.

Working on this now, I think we don't need a warning in the bochs_uses_mmio()
helper because we should never get here with !IS_ENABLED(CONFIG_HAS_IOPORT)
at runtime thanks to the check added in bochs_hw_init(). This also takes
care of my original worry that we might try writeb()/readb() with an invalid
bochs->mmio value. I'll sent a v9 with the helper added and #ifdefs's removed.

Thanks,
Niklas