linux-kernel - [PATCH v2] firmware: qemu_fw_cfg: Do not hard depend on CONFIG_HAS_IOPORT

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Message-ID: <24142953.6Emhk5qWAg@fvogt-thinkpad>
Date: Mon, 03 Nov 2025 15:11:05 +0100
From: Fabian Vogt <fvogt@...e.de>
To: "Michael S. Tsirkin" <mst@...hat.com>, Gabriel Somlo <somlo@....edu>
Cc: qemu-devel@...gnu.org, linux-kernel@...r.kernel.org,
 Takashi Iwai <tiwai@...e.de>
Subject:
 [PATCH v2] firmware: qemu_fw_cfg: Do not hard depend on CONFIG_HAS_IOPORT_MAP

Some configs have CONFIG_NO_IOPORT_MAP=y but support qemu_fw_cfg over
MMIO. Currently the qemu_fw_cfg module can't be built for those as it
needs HAS_IOPORT_MAP=y for ioport remapping.

This patch allows to build qemu_fw_cfg in those cases. If
CONFIG_HAS_IOPORT_MAP=n, qemu_fw_cfg is just built without support for
ioport based access.

Signed-off-by: Fabian Vogt <fvogt@...e.de>
---
v2: Guard ioport_unmap as well, which makes it work on archs like arm64
in the !PCI case. Unlike arm, arm64 has no stub for ioport_unmap.
Reword description.

 drivers/firmware/Kconfig       | 1 -
 drivers/firmware/qemu_fw_cfg.c | 7 +++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index bbd2155d8483..91442f85f0f0 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -122,7 +122,6 @@ config RASPBERRYPI_FIRMWARE
 config FW_CFG_SYSFS
 	tristate "QEMU fw_cfg device support in sysfs"
 	depends on SYSFS && (ARM || ARM64 || PARISC || PPC_PMAC || RISCV || SPARC || X86)
-	depends on HAS_IOPORT_MAP
 	default n
 	help
 	  Say Y or M here to enable the exporting of the QEMU firmware
diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
index 0eebd572f9a5..fa4385339824 100644
--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -204,8 +204,10 @@ static void fw_cfg_io_cleanup(void)
 		iounmap(fw_cfg_dev_base);
 		release_mem_region(fw_cfg_p_base, fw_cfg_p_size);
 	} else {
+#ifdef CONFIG_HAS_IOPORT_MAP
 		ioport_unmap(fw_cfg_dev_base);
 		release_region(fw_cfg_p_base, fw_cfg_p_size);
+#endif
 	}
 }
 
@@ -258,6 +260,7 @@ static int fw_cfg_do_platform_probe(struct platform_device *pdev)
 			return -EFAULT;
 		}
 	} else {
+#ifdef CONFIG_HAS_IOPORT_MAP
 		if (!request_region(fw_cfg_p_base,
 				    fw_cfg_p_size, "fw_cfg_io"))
 			return -EBUSY;
@@ -266,6 +269,10 @@ static int fw_cfg_do_platform_probe(struct platform_device *pdev)
 			release_region(fw_cfg_p_base, fw_cfg_p_size);
 			return -EFAULT;
 		}
+#else
+		dev_err(&pdev->dev, "IO region given but CONFIG_HAS_IOPORT_MAP=n");
+		return -EINVAL;
+#endif
 	}
 
 	/* were custom register offsets provided (e.g. on the command line)? */
-- 
2.51.1