[PATCH v2 0/5] Congatec Board Controller: Add storage devices support

[PATCH v2 0/5] Congatec Board Controller: Add storage devices support

[Thomas Richard (congatec GmbH)]

Second iteration and nothing fancy, I just fixed a typo in CGBC BIOS EEPROM
label, and added a patch to make cgbc_devs (MFD cells) const in MFD driver.

Signed-off-by: Thomas Richard (congatec GmbH) <thomas.richard@bootlin.com>
---
Changes in v2:
- i2c: fix typo in CGBC BIOS EEPROM labeli.
- mfd: make cgbc_devs const
- Link to v1: https://patch.msgid.link/20260804-cgbc-i2c-storage-devices-support-v1-0-fed38510671c@bootlin.com

To: Thomas Richard <thomas.richard@bootlin.com>
To: Lee Jones <lee@kernel.org>
To: Andi Shyti <andi.shyti@kernel.org>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Werner Gartner <Werner.Gartner@congatec.com>
Cc: mfd@lists.linux.dev
Cc: linux-kernel@vger.kernel.org
Cc: linux-i2c@vger.kernel.org

---
Thomas Richard (congatec GmbH) (5):
      mfd: cgbc: Fix use of negative error code as valid session handle
      mfd: cgbc: Make cgbc_devs const
      i2c: cgbc: Add virtual I2C bus support
      mfd: cgbc: Add virtual I2C bus support
      i2c: cgbc: Add virtual storage devices on the virtual I2C bus

 drivers/i2c/busses/i2c-cgbc.c | 174 ++++++++++++++++++++++++++++++++++++++++--
 drivers/mfd/cgbc-core.c       |   9 ++-
 2 files changed, 175 insertions(+), 8 deletions(-)
---
base-commit: 498c377a1ca412502649484c7b1788d5d328fc85
change-id: 20260717-cgbc-i2c-storage-devices-support-b3ee7cea3320

Best regards,
--  
Thomas Richard (congatec GmbH) <thomas.richard@bootlin.com>

[PATCH v2 1/5] mfd: cgbc: Fix use of negative error code as valid session handle

[Thomas Richard (congatec GmbH)]

The cgbc_session_command() return value was directly cast to u8 and used
as session handle without error checking. Casting a negative error to u8
produces a valid-looking session handle. So check if return value is
positive before to cast and use it.

Cc: stable@vger.kernel.org
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260713-cgbc-core-fix-cgbc-remove-v1-1-79274ad62b3a%40bootlin.com?part=1
Fixes: 6f1067cfbee7 ("mfd: Add Congatec Board Controller driver")
Signed-off-by: Thomas Richard (congatec GmbH) <thomas.richard@bootlin.com>
---
 drivers/mfd/cgbc-core.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/mfd/cgbc-core.c b/drivers/mfd/cgbc-core.c
index 2becaf797646..4a409234e66c 100644
--- a/drivers/mfd/cgbc-core.c
+++ b/drivers/mfd/cgbc-core.c
@@ -103,7 +103,11 @@ static int cgbc_session_request(struct cgbc_device_data *cgbc)
 	if (ret)
 		return dev_err_probe(cgbc->dev, ret, "device not found or not ready\n");
 
-	cgbc->session = cgbc_session_command(cgbc, CGBC_SESSION_CMD_REQUEST);
+	ret = cgbc_session_command(cgbc, CGBC_SESSION_CMD_REQUEST);
+	if (ret < 0)
+		return dev_err_probe(cgbc->dev, ret, "session handle request timed out\n");
+
+	cgbc->session = ret;
 
 	/* The Board Controller sent us a wrong session handle, we cannot communicate with it */
 	if (cgbc->session < CGBC_SESSION_VALID_MIN || cgbc->session > CGBC_SESSION_VALID_MAX)

-- 
2.53.0

Re: [PATCH v2 0/5] Congatec Board Controller: Add storage devices support

[Thomas Richard]

On 8/11/26 6:15 PM, Thomas Richard (congatec GmbH) wrote:
> Second iteration and nothing fancy, I just fixed a typo in CGBC BIOS EEPROM
> label, and added a patch to make cgbc_devs (MFD cells) const in MFD driver.
Please ignore this version. Following the discussion with Lee on
hard-coding the cell ID, I'm finally preparing a new version of this
series which switches to PLATFORM_DEVID_AUTO before to add the virtual
bus and virtual storage devices support.

Also IMO having the i2c_board_info struct in the I2C bus driver is a bit
odd. The I2C devices topology on the virtual bus can be different,
depending the Board Controller. I think this complexity shall be handled
on MFD side.

At the end I should have a more generic I2C bus driver, and
platform_data will be used to pass all parameters (including I2C devices
to register on the I2C bus) to the I2C bus driver.

Best Regards,
Thomas

Re: [PATCH v2 1/5] mfd: cgbc: Fix use of negative error code as valid session handle

[Lee Jones]

On Tue, 11 Aug 2026, Thomas Richard (congatec GmbH) wrote:

> The cgbc_session_command() return value was directly cast to u8 and used
> as session handle without error checking. Casting a negative error to u8
> produces a valid-looking session handle. So check if return value is
> positive before to cast and use it.
> 
> Cc: stable@vger.kernel.org
> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Closes: https://sashiko.dev/#/patchset/20260713-cgbc-core-fix-cgbc-remove-v1-1-79274ad62b3a%40bootlin.com?part=1
> Fixes: 6f1067cfbee7 ("mfd: Add Congatec Board Controller driver")
> Signed-off-by: Thomas Richard (congatec GmbH) <thomas.richard@bootlin.com>
> ---
>  drivers/mfd/cgbc-core.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mfd/cgbc-core.c b/drivers/mfd/cgbc-core.c
> index 2becaf797646..4a409234e66c 100644
> --- a/drivers/mfd/cgbc-core.c
> +++ b/drivers/mfd/cgbc-core.c
> @@ -103,7 +103,11 @@ static int cgbc_session_request(struct cgbc_device_data *cgbc)
>  	if (ret)
>  		return dev_err_probe(cgbc->dev, ret, "device not found or not ready\n");
>  
> -	cgbc->session = cgbc_session_command(cgbc, CGBC_SESSION_CMD_REQUEST);
> +	ret = cgbc_session_command(cgbc, CGBC_SESSION_CMD_REQUEST);
> +	if (ret < 0)
> +		return dev_err_probe(cgbc->dev, ret, "session handle request timed out\n");

Can we make this a bit more user friendly?

"Failed to start XYZ session"?

> +
> +	cgbc->session = ret;
>  
>  	/* The Board Controller sent us a wrong session handle, we cannot communicate with it */
>  	if (cgbc->session < CGBC_SESSION_VALID_MIN || cgbc->session > CGBC_SESSION_VALID_MAX)
> 
> -- 
> 2.53.0
> 

-- 
Lee Jones

Re: [PATCH v2 1/5] mfd: cgbc: Fix use of negative error code as valid session handle

[Lee Jones]

On Wed, 02 Sep 2026, Lee Jones wrote:

> On Tue, 11 Aug 2026, Thomas Richard (congatec GmbH) wrote:
> 
> > The cgbc_session_command() return value was directly cast to u8 and used
> > as session handle without error checking. Casting a negative error to u8
> > produces a valid-looking session handle. So check if return value is
> > positive before to cast and use it.
> > 
> > Cc: stable@vger.kernel.org
> > Reported-by: Sashiko <sashiko-bot@kernel.org>
> > Closes: https://sashiko.dev/#/patchset/20260713-cgbc-core-fix-cgbc-remove-v1-1-79274ad62b3a%40bootlin.com?part=1
> > Fixes: 6f1067cfbee7 ("mfd: Add Congatec Board Controller driver")
> > Signed-off-by: Thomas Richard (congatec GmbH) <thomas.richard@bootlin.com>
> > ---
> >  drivers/mfd/cgbc-core.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mfd/cgbc-core.c b/drivers/mfd/cgbc-core.c
> > index 2becaf797646..4a409234e66c 100644
> > --- a/drivers/mfd/cgbc-core.c
> > +++ b/drivers/mfd/cgbc-core.c
> > @@ -103,7 +103,11 @@ static int cgbc_session_request(struct cgbc_device_data *cgbc)
> >  	if (ret)
> >  		return dev_err_probe(cgbc->dev, ret, "device not found or not ready\n");
> >  
> > -	cgbc->session = cgbc_session_command(cgbc, CGBC_SESSION_CMD_REQUEST);
> > +	ret = cgbc_session_command(cgbc, CGBC_SESSION_CMD_REQUEST);
> > +	if (ret < 0)
> > +		return dev_err_probe(cgbc->dev, ret, "session handle request timed out\n");
> 
> Can we make this a bit more user friendly?
> 
> "Failed to start XYZ session"?

The other two MFD patches are fine.

-- 
Lee Jones