[PATCH v3 0/3] cdrom: gdrom: fix block I/O and capacity setting

[PATCH v3 0/3] cdrom: gdrom: fix block I/O and capacity setting

[Florian Fuchs]

Hi all,

This series fixes a gdrom driver Oops due to bad MMIO register access and
fixes the missing updates of the block layer gendisk capacity that
prevented ISO9660 mounts from working. It fixes also the case of disc
swapping by sending the Test Unit command prior to cdrom_open().

The change was tested on real Sega Dreamcast devices (PAL-E, NTSC-J,
NTSC-U) with physical CD-R discs and with GDEMU emulated discs. Before:
Oops on mount and an unusable drive. After: Successfully able to mount
and use the inserted medium.

Thanks,
Florian
---
v2->v3: Added patch "cdrom: gdrom: verify device access after disc swap"
        from Artur Rojek to also handle the disc swap case reliably. And
        added Acked-by, Reviewed-by from v2 to the respective patches.
        Also handle the GDROM case in gdrom_update_capacity().
v1->v2: for "cdrom: gdrom: replace port I/O with MMIO accessors": Don't
        use helper functions with io.*_rep(), but writesw() and readsw()
        local in the respective functions. Improved failure case of
        gdrom_update_capacity() in gdrom_bdops_open().

v2: https://lore.kernel.org/linux-sh/20260419162823.2829286-1-fuchsfl@gmail.com/
v1: https://lore.kernel.org/linux-sh/20260405082330.4104672-1-fuchsfl@gmail.com/

Artur Rojek (1):
  cdrom: gdrom: verify device access after disc swap

Florian Fuchs (2):
  cdrom: gdrom: replace port I/O with MMIO accessors
  cdrom: gdrom: update gendisk capacity on open

 drivers/cdrom/gdrom.c | 65 ++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 61 insertions(+), 4 deletions(-)


base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
-- 
2.43.0

[PATCH v3 1/3] cdrom: gdrom: replace port I/O with MMIO accessors

[Florian Fuchs]

GDROM_DATA_REG is a memory-mapped data register, but the driver uses
outsw() and insw() only for this register. Replace this with MMIO
accessors readsw() / writesw().

Before, it oopsed accessing the data register, as the io_port_base
P2SEG gets added to the argument in outsw() / insw(), which leads to an
unusable drive:

        BUG: unable to handle kernel paging request at 405f7080
        PC: [<8c28d5b4>] gdrom_spicommand+0x6c/0xb0

Signed-off-by: Florian Fuchs <fuchsfl@gmail.com>
Acked-by: Artur Rojek <contact@artur-rojek.eu>
Reviewed-by: Adrian McMenamin <adrianmcmenamin@gmail.com>
---
v2->v3: no functional change. Added Acked-by from Artur Rojek.
        Added Reviewed-by tag from Adrian McMenamin.
v1->v2: Don't use helper functions with io.*_rep(), but writesw() and
        readsw() local in the respective functions

v2: https://lore.kernel.org/linux-sh/20260419162823.2829286-2-fuchsfl@gmail.com/
v1: https://lore.kernel.org/linux-sh/20260405082330.4104672-2-fuchsfl@gmail.com/

 drivers/cdrom/gdrom.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/cdrom/gdrom.c b/drivers/cdrom/gdrom.c
index 4ba4dd06cbf4..094d55b2d004 100644
--- a/drivers/cdrom/gdrom.c
+++ b/drivers/cdrom/gdrom.c
@@ -198,7 +198,7 @@ static void gdrom_spicommand(void *spi_string, int buflen)
 		gdrom_getsense(NULL);
 		return;
 	}
-	outsw(GDROM_DATA_REG, cmd, 6);
+	writesw((void __iomem *)GDROM_DATA_REG, cmd, 6);
 }
 
 
@@ -282,7 +282,7 @@ static int gdrom_readtoc_cmd(struct gdromtoc *toc, int session)
 		err = -EINVAL;
 		goto cleanup_readtoc;
 	}
-	insw(GDROM_DATA_REG, toc, tocsize/2);
+	readsw((void __iomem *)GDROM_DATA_REG, toc, tocsize / 2);
 	if (gd.status & 0x01)
 		err = -EINVAL;
 
@@ -433,7 +433,7 @@ static int gdrom_getsense(short *bufstring)
 		GDROM_DEFAULT_TIMEOUT);
 	if (gd.pending)
 		goto cleanup_sense;
-	insw(GDROM_DATA_REG, &sense, sense_command->buflen/2);
+	readsw((void __iomem *)GDROM_DATA_REG, &sense, sense_command->buflen / 2);
 	if (sense[1] & 40) {
 		pr_info("Drive not ready - command aborted\n");
 		goto cleanup_sense;
@@ -612,7 +612,7 @@ static blk_status_t gdrom_readdisk_dma(struct request *req)
 		cpu_relax();
 	gd.pending = 1;
 	gd.transfer = 1;
-	outsw(GDROM_DATA_REG, &read_command->cmd, 6);
+	writesw((void __iomem *)GDROM_DATA_REG, read_command->cmd, 6);
 	timeout = jiffies + HZ / 2;
 	/* Wait for any pending DMA to finish */
 	while (__raw_readb(GDROM_DMA_STATUS_REG) &&
-- 
2.43.0

[PATCH v3 2/3] cdrom: gdrom: update gendisk capacity on open

[Florian Fuchs]

Update the gendisk capacity of the media. Without the capacity, the block
reads fail before reaching the request queue, which prevented ISO9660
mounts. Refresh the capacity from the TOC leadout in gdrom_bdops_open()
so it checks the inserted media.

Signed-off-by: Florian Fuchs <fuchsfl@gmail.com>
---
v2->v3: Also add quirk to handle proprietary GDROMs, using the same
        mechanic like in gdrom_get_last_session() try session 1 first
	for GDROM, then session 0 for CDROMs. Dropped Acked-By due to
	code change.
v1->v2: no change for gdrom_update_capacity(), but for
        gdrom_bdops_open(): handle the failure case when
        gdrom_update_capacity() fails but previous cdrom_open() succeeded,
        to cleanup the successful cdrom_open() with cdrom_release()

v2: https://lore.kernel.org/linux-sh/20260419162823.2829286-3-fuchsfl@gmail.com/
v1: https://lore.kernel.org/linux-sh/20260405082330.4104672-3-fuchsfl@gmail.com/

 drivers/cdrom/gdrom.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/cdrom/gdrom.c b/drivers/cdrom/gdrom.c
index 094d55b2d004..1e73617b39ac 100644
--- a/drivers/cdrom/gdrom.c
+++ b/drivers/cdrom/gdrom.c
@@ -474,6 +474,27 @@ static const struct cdrom_device_ops gdrom_ops = {
 				  CDC_RESET | CDC_DRIVE_STATUS | CDC_CD_R,
 };
 
+static int gdrom_update_capacity(void)
+{
+	sector_t cap;
+	int ret;
+
+	if (gdrom_drivestatus(gd.cd_info, CDSL_CURRENT) != CDS_DISC_OK) {
+		set_capacity(gd.disk, 0);
+		return -ENOMEDIUM;
+	}
+	ret = gdrom_readtoc_cmd(gd.toc, 1);
+	if (ret)
+		ret = gdrom_readtoc_cmd(gd.toc, 0);
+	if (ret) {
+		set_capacity(gd.disk, 0);
+		return ret;
+	}
+	cap = (sector_t)get_entry_lba(gd.toc->leadout) * GD_TO_BLK;
+	set_capacity(gd.disk, cap);
+	return 0;
+}
+
 static int gdrom_bdops_open(struct gendisk *disk, blk_mode_t mode)
 {
 	int ret;
@@ -482,6 +503,12 @@ static int gdrom_bdops_open(struct gendisk *disk, blk_mode_t mode)
 
 	mutex_lock(&gdrom_mutex);
 	ret = cdrom_open(gd.cd_info, mode);
+	if (ret)
+		goto out;
+	ret = gdrom_update_capacity();
+	if (ret)
+		cdrom_release(gd.cd_info);
+out:
 	mutex_unlock(&gdrom_mutex);
 	return ret;
 }
-- 
2.43.0

[PATCH v3 3/3] cdrom: gdrom: verify device access after disc swap

[Florian Fuchs]

From: Artur Rojek <contact@artur-rojek.eu>

To ready the drive for cdrom_open(), this driver sends a spin disc
command. However, if the cd lid has been opened and the disc de-spinned,
the very next SPI command will return UNIT_ATTENTION sense error,
resulting in a failure to mount the disc.

Fix this by sending a dummy TEST_UNIT command, which will catch the
above error, and allow subsequent commands to execute correctly.

Signed-off-by: Artur Rojek <contact@artur-rojek.eu>
Signed-off-by: Florian Fuchs <fuchsfl@gmail.com>
---
v3: new patch added from Artur Rojek and also verified that it works.

 drivers/cdrom/gdrom.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/cdrom/gdrom.c b/drivers/cdrom/gdrom.c
index 1e73617b39ac..21ef4657dd2b 100644
--- a/drivers/cdrom/gdrom.c
+++ b/drivers/cdrom/gdrom.c
@@ -219,6 +219,33 @@ static char gdrom_execute_diagnostic(void)
 	return __raw_readb(GDROM_ERROR_REG);
 }
 
+/*
+ * Test unit command
+ * byte 0 = 0x0
+ *
+ * This command verifies whether device can be accessed.
+ *
+ * -EIO indicates that device is not ready for operation.
+ */
+static int gdrom_test_unit_cmd(void)
+{
+	struct packet_command *test_command;
+
+	test_command = kzalloc_obj(struct packet_command);
+	if (!test_command)
+		return -ENOMEM;
+	test_command->cmd[0] = 0x0;
+	test_command->buflen = 0;
+	gd.pending = 1;
+	gdrom_packetcommand(gd.cd_info, test_command);
+	wait_event_interruptible_timeout(command_queue, gd.pending == 0,
+					 GDROM_DEFAULT_TIMEOUT);
+	gd.pending = 0;
+	kfree(test_command);
+
+	return gd.status & 0x1 ? -EIO : 0;
+}
+
 /*
  * Prepare disk command
  * byte 0 = 0x70
@@ -353,6 +380,9 @@ static int gdrom_get_last_session(struct cdrom_device_info *cd_info,
 
 static int gdrom_open(struct cdrom_device_info *cd_info, int purpose)
 {
+	/* Sink pending UNIT_ATTENTION sense error after a disc swap. */
+	(void)gdrom_test_unit_cmd();
+
 	/* spin up the disk */
 	return gdrom_preparedisk_cmd();
 }
-- 
2.43.0

Re: [PATCH v3 2/3] cdrom: gdrom: update gendisk capacity on open

[Artur Rojek]

On 2026-04-23 21:41, Florian Fuchs wrote:
> Update the gendisk capacity of the media. Without the capacity, the 
> block
> reads fail before reaching the request queue, which prevented ISO9660
> mounts. Refresh the capacity from the TOC leadout in gdrom_bdops_open()
> so it checks the inserted media.
> 
> Signed-off-by: Florian Fuchs <fuchsfl@gmail.com>

Hey Florian,
thanks for v3. Verified on real hardware.

> ---
> v2->v3: Also add quirk to handle proprietary GDROMs, using the same
>         mechanic like in gdrom_get_last_session() try session 1 first
> 	for GDROM, then session 0 for CDROMs. Dropped Acked-By due to
> 	code change.
> v1->v2: no change for gdrom_update_capacity(), but for
>         gdrom_bdops_open(): handle the failure case when
>         gdrom_update_capacity() fails but previous cdrom_open() 
> succeeded,
>         to cleanup the successful cdrom_open() with cdrom_release()
> 
> v2: 
> https://lore.kernel.org/linux-sh/20260419162823.2829286-3-fuchsfl@gmail.com/
> v1: 
> https://lore.kernel.org/linux-sh/20260405082330.4104672-3-fuchsfl@gmail.com/
> 
>  drivers/cdrom/gdrom.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/drivers/cdrom/gdrom.c b/drivers/cdrom/gdrom.c
> index 094d55b2d004..1e73617b39ac 100644
> --- a/drivers/cdrom/gdrom.c
> +++ b/drivers/cdrom/gdrom.c
> @@ -474,6 +474,27 @@ static const struct cdrom_device_ops gdrom_ops = {
>  				  CDC_RESET | CDC_DRIVE_STATUS | CDC_CD_R,
>  };
> 
> +static int gdrom_update_capacity(void)
> +{
> +	sector_t cap;
> +	int ret;
> +
> +	if (gdrom_drivestatus(gd.cd_info, CDSL_CURRENT) != CDS_DISC_OK) {
> +		set_capacity(gd.disk, 0);
> +		return -ENOMEDIUM;
> +	}
> +	ret = gdrom_readtoc_cmd(gd.toc, 1);
> +	if (ret)
> +		ret = gdrom_readtoc_cmd(gd.toc, 0);
> +	if (ret) {
> +		set_capacity(gd.disk, 0);
> +		return ret;
> +	}

Since you already clobber the return value of
gdrom_readtoc_cmd(gd.toc, 1), then how about make it even simpler:

>        if (gdrom_readtoc_cmd(gd.toc, 1) && gdrom_readtoc_cmd(gd.toc, 
> 0)) {
>                set_capacity(gd.disk, 0);
>                return -EINVAL;
>        }

With or without the above change:

Acked-by: Artur Rojek <contact@artur-rojek.eu>

Cheers,
Artur

> +	cap = (sector_t)get_entry_lba(gd.toc->leadout) * GD_TO_BLK;
> +	set_capacity(gd.disk, cap);
> +	return 0;
> +}
> +
>  static int gdrom_bdops_open(struct gendisk *disk, blk_mode_t mode)
>  {
>  	int ret;
> @@ -482,6 +503,12 @@ static int gdrom_bdops_open(struct gendisk *disk, 
> blk_mode_t mode)
> 
>  	mutex_lock(&gdrom_mutex);
>  	ret = cdrom_open(gd.cd_info, mode);
> +	if (ret)
> +		goto out;
> +	ret = gdrom_update_capacity();
> +	if (ret)
> +		cdrom_release(gd.cd_info);
> +out:
>  	mutex_unlock(&gdrom_mutex);
>  	return ret;
>  }