[PATCH v1 0/8] zorro: Improve handling of pointers in zorro_device_id::driver_data

[PATCH v1 0/8] zorro: Improve handling of pointers in zorro_device_id::driver_data

[Uwe Kleine-König (The Capable Hub)]

Hello,

this series is about improving the handling of pointers in struct
zorro_device_id's driver_data.

While it's ok on all current Linux platforms to store a pointer in an
unsigned long variable, it involves casting that loses type information.
This can be nicely seen in patch #7 where after profiting from patch #6
the compiler notices a missing const.

Preparing for that change, all zorro_device_ids are converted to use
named initializers, which is also a nice cleanup that could stand for
itself, as it improves readability for humans. (That is necessary
because an anonymous union can be initialized by name, but not using a
list initializer.)

My motivation for this series is the CHERI hardware extension. With that
pointers are bigger than longs and thus you cannot store pointers in
zorro_device_id::driver_data. So this series is also about getting
support for CHERI into the mainline, but I hope the clean up effects
mentioned above are justification enough to accept this series.

The dependencies in this series are as follows:

 - Patch #5 depends on #1, #2
 - Patches #7 and #8 depend on patch #6.

So if the ata maintainers agreed to merge their patch #1 via scsi, and
Geert agrees to patch #5 and that it's also merged via scsi, patches #1,
#2, #6 and #7 can go in without further coordination.

Patches #3, #4 and #5 are only about using the same initialization style
for all zorro_device_id and can go in without coordination.

Best regards
Uwe

Uwe Kleine-König (The Capable Hub) (8):
  ata: pata_budda: Use named initializer for zorro_device_id
  scsi: Use named initializer for zorro_device_id
  net: Use named initializer for zorro_device_id arrays
  i2c: icy: Use named initializer for zorro_device_id arrays
  video: fm2fb: Use named initializer for zorro_device_id array
  zorro: Simplify storing pointers in device id struct
  scsi: zorro7xx: Make use of struct zorro_device_id::driver_data_ptr
  video: cirrusfb: Make use of struct zorro_device_id::driver_data_ptr

 drivers/ata/pata_buddha.c             |  8 ++++----
 drivers/i2c/busses/i2c-icy.c          |  4 ++--
 drivers/net/ethernet/8390/hydra.c     |  4 ++--
 drivers/net/ethernet/8390/xsurf100.c  |  4 ++--
 drivers/net/ethernet/8390/zorro8390.c |  6 +++---
 drivers/net/ethernet/amd/a2065.c      |  8 ++++----
 drivers/net/ethernet/amd/ariadne.c    |  4 ++--
 drivers/scsi/a2091.c                  |  6 +++---
 drivers/scsi/gvp11.c                  | 17 ++++++++--------
 drivers/scsi/zorro7xx.c               | 16 +++++++--------
 drivers/scsi/zorro_esp.c              |  2 +-
 drivers/video/fbdev/cirrusfb.c        | 28 +++++++++++++--------------
 drivers/video/fbdev/fm2fb.c           |  6 +++---
 include/linux/mod_devicetable.h       |  6 +++++-
 14 files changed, 62 insertions(+), 57 deletions(-)


base-commit: d387b06f7c15b4639244ad66b4b0900c6a02b430
-- 
2.47.3

[PATCH v1 5/8] video: fm2fb: Use named initializer for zorro_device_id array

[Uwe Kleine-König (The Capable Hub)]

Using named initializers is more explicit and thus easier to parse for a
human.

While touching this array, drop the explicit zero from the list terminator.

This change doesn't introduce changes to the compiled zorro_device_id
array.

Signed-off-by: Uwe Kleine-König (The Capable Hub) <u.kleine-koenig@baylibre.com>
---
 drivers/video/fbdev/fm2fb.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/video/fbdev/fm2fb.c b/drivers/video/fbdev/fm2fb.c
index 25d2e716edf2..a62c8d86bf69 100644
--- a/drivers/video/fbdev/fm2fb.c
+++ b/drivers/video/fbdev/fm2fb.c
@@ -212,9 +212,9 @@ static int fm2fb_setcolreg(u_int regno, u_int red, u_int green, u_int blue,
 static int fm2fb_probe(struct zorro_dev *z, const struct zorro_device_id *id);
 
 static const struct zorro_device_id fm2fb_devices[] = {
-	{ ZORRO_PROD_BSC_FRAMEMASTER_II },
-	{ ZORRO_PROD_HELFRICH_RAINBOW_II },
-	{ 0 }
+	{ .id = ZORRO_PROD_BSC_FRAMEMASTER_II },
+	{ .id = ZORRO_PROD_HELFRICH_RAINBOW_II },
+	{ }
 };
 MODULE_DEVICE_TABLE(zorro, fm2fb_devices);
 
-- 
2.47.3

[PATCH v1 6/8] zorro: Simplify storing pointers in device id struct

[Uwe Kleine-König (The Capable Hub)]

Technically it is fine (on all current Linux architectures) to store a
pointer in an unsigned long variable. However this needs explicit
casting which is an easy source for type mismatches.

By replacing the plain unsigned long .driver_data in struct
zorro_device_id by an anonymous union, most of the casting can be
dropped. There is still some implicit casting involved (between a void *
and a driver specific pointer type), but that's better than the approach
to store a pointer in an unsigned long variable as this doesn't lose the
information that the data being pointed to is const.

All users of struct zorro_device_id are initialized in a way that is
compatible with the new definition, so no adaptions are needed there.

Signed-off-by: Uwe Kleine-König (The Capable Hub) <u.kleine-koenig@baylibre.com>
---
 include/linux/mod_devicetable.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index 3b0c9a251a2e..2673a1bd82c4 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -640,7 +640,11 @@ struct mdio_device_id {
 
 struct zorro_device_id {
 	__u32 id;			/* Device ID or ZORRO_WILDCARD */
-	kernel_ulong_t driver_data;	/* Data private to the driver */
+	union {
+		/* Data private to the driver */
+		kernel_ulong_t driver_data;
+		const void *driver_data_ptr;
+	};
 };
 
 #define ZORRO_WILDCARD			(0xffffffff)	/* not official */
-- 
2.47.3

[PATCH v1 8/8] video: cirrusfb: Make use of struct zorro_device_id::driver_data_ptr

[Uwe Kleine-König (The Capable Hub)]

Usage of .driver_data_ptr allows to drop several casts and so make the
driver a bit more type safe.

While touching the zorro_device_id array, drop an unneeded explicit zero
in the list terminator.

Signed-off-by: Uwe Kleine-König (The Capable Hub) <u.kleine-koenig@baylibre.com>
---
 drivers/video/fbdev/cirrusfb.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/drivers/video/fbdev/cirrusfb.c b/drivers/video/fbdev/cirrusfb.c
index 2693b5cc053f..7e07e775b393 100644
--- a/drivers/video/fbdev/cirrusfb.c
+++ b/drivers/video/fbdev/cirrusfb.c
@@ -321,25 +321,25 @@ static const struct zorrocl zcl_picasso4_z2 = {
 
 static const struct zorro_device_id cirrusfb_zorro_table[] = {
 	{
-		.id		= ZORRO_PROD_HELFRICH_SD64_REG,
-		.driver_data	= (unsigned long)&zcl_sd64,
+		.id = ZORRO_PROD_HELFRICH_SD64_REG,
+		.driver_data_ptr = &zcl_sd64,
 	}, {
-		.id		= ZORRO_PROD_HELFRICH_PICCOLO_REG,
-		.driver_data	= (unsigned long)&zcl_piccolo,
+		.id = ZORRO_PROD_HELFRICH_PICCOLO_REG,
+		.driver_data_ptr = &zcl_piccolo,
 	}, {
-		.id	= ZORRO_PROD_VILLAGE_TRONIC_PICASSO_II_II_PLUS_REG,
-		.driver_data	= (unsigned long)&zcl_picasso,
+		.id = ZORRO_PROD_VILLAGE_TRONIC_PICASSO_II_II_PLUS_REG,
+		.driver_data_ptr = &zcl_picasso,
 	}, {
-		.id		= ZORRO_PROD_GVP_EGS_28_24_SPECTRUM_REG,
-		.driver_data	= (unsigned long)&zcl_spectrum,
+		.id = ZORRO_PROD_GVP_EGS_28_24_SPECTRUM_REG,
+		.driver_data_ptr = &zcl_spectrum,
 	}, {
-		.id		= ZORRO_PROD_VILLAGE_TRONIC_PICASSO_IV_Z3,
-		.driver_data	= (unsigned long)&zcl_picasso4_z3,
+		.id = ZORRO_PROD_VILLAGE_TRONIC_PICASSO_IV_Z3,
+		.driver_data_ptr = &zcl_picasso4_z3,
 	}, {
-		.id		= ZORRO_PROD_VILLAGE_TRONIC_PICASSO_IV_Z2_REG,
-		.driver_data	= (unsigned long)&zcl_picasso4_z2,
+		.id = ZORRO_PROD_VILLAGE_TRONIC_PICASSO_IV_Z2_REG,
+		.driver_data_ptr = &zcl_picasso4_z2,
 	},
-	{ 0 }
+	{ }
 };
 MODULE_DEVICE_TABLE(zorro, cirrusfb_zorro_table);
 #endif /* CONFIG_ZORRO */
@@ -2208,7 +2208,7 @@ static int cirrusfb_zorro_register(struct zorro_dev *z,
 	if (!info)
 		return -ENOMEM;
 
-	zcl = (const struct zorrocl *)ent->driver_data;
+	zcl = ent->driver_data_ptr;
 	btype = zcl->type;
 	regbase = zorro_resource_start(z) + zcl->regoffset;
 	ramsize = zcl->ramsize;
-- 
2.47.3

Re: [PATCH v1 0/8] zorro: Improve handling of pointers in zorro_device_id::driver_data

[Geert Uytterhoeven]

Hi Uwe,

On Tue, 26 May 2026 at 16:17, Uwe Kleine-König (The Capable Hub)
<u.kleine-koenig@baylibre.com> wrote:
> this series is about improving the handling of pointers in struct
> zorro_device_id's driver_data.
>
> While it's ok on all current Linux platforms to store a pointer in an
> unsigned long variable, it involves casting that loses type information.
> This can be nicely seen in patch #7 where after profiting from patch #6
> the compiler notices a missing const.
>
> Preparing for that change, all zorro_device_ids are converted to use
> named initializers, which is also a nice cleanup that could stand for
> itself, as it improves readability for humans. (That is necessary
> because an anonymous union can be initialized by name, but not using a
> list initializer.)
>
> My motivation for this series is the CHERI hardware extension. With that
> pointers are bigger than longs and thus you cannot store pointers in
> zorro_device_id::driver_data. So this series is also about getting
> support for CHERI into the mainline, but I hope the clean up effects
> mentioned above are justification enough to accept this series.

Thanks for your series!

> The dependencies in this series are as follows:
>
>  - Patch #5 depends on #1, #2

s/5/6/?

>  - Patches #7 and #8 depend on patch #6.
>
> So if the ata maintainers agreed to merge their patch #1 via scsi, and
> Geert agrees to patch #5 and that it's also merged via scsi, patches #1,

s/5/6/?

> #2, #6 and #7 can go in without further coordination.
>
> Patches #3, #4 and #5 are only about using the same initialization style
> for all zorro_device_id and can go in without coordination.
>
> Best regards
> Uwe
>
> Uwe Kleine-König (The Capable Hub) (8):
>   ata: pata_budda: Use named initializer for zorro_device_id
>   scsi: Use named initializer for zorro_device_id
>   net: Use named initializer for zorro_device_id arrays
>   i2c: icy: Use named initializer for zorro_device_id arrays
>   video: fm2fb: Use named initializer for zorro_device_id array
>   zorro: Simplify storing pointers in device id struct
>   scsi: zorro7xx: Make use of struct zorro_device_id::driver_data_ptr
>   video: cirrusfb: Make use of struct zorro_device_id::driver_data_ptr

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v1 0/8] zorro: Improve handling of pointers in zorro_device_id::driver_data

[Uwe Kleine-König (The Capable Hub)]

[-- Attachment #1: Type: text/plain, Size: 1732 bytes --]

On Tue, May 26, 2026 at 05:01:48PM +0200, Geert Uytterhoeven wrote:
> Hi Uwe,
> 
> On Tue, 26 May 2026 at 16:17, Uwe Kleine-König (The Capable Hub)
> <u.kleine-koenig@baylibre.com> wrote:
> > this series is about improving the handling of pointers in struct
> > zorro_device_id's driver_data.
> >
> > While it's ok on all current Linux platforms to store a pointer in an
> > unsigned long variable, it involves casting that loses type information.
> > This can be nicely seen in patch #7 where after profiting from patch #6
> > the compiler notices a missing const.
> >
> > Preparing for that change, all zorro_device_ids are converted to use
> > named initializers, which is also a nice cleanup that could stand for
> > itself, as it improves readability for humans. (That is necessary
> > because an anonymous union can be initialized by name, but not using a
> > list initializer.)
> >
> > My motivation for this series is the CHERI hardware extension. With that
> > pointers are bigger than longs and thus you cannot store pointers in
> > zorro_device_id::driver_data. So this series is also about getting
> > support for CHERI into the mainline, but I hope the clean up effects
> > mentioned above are justification enough to accept this series.
> 
> Thanks for your series!
> 
> > The dependencies in this series are as follows:
> >
> >  - Patch #5 depends on #1, #2
> 
> s/5/6/?
> 
> >  - Patches #7 and #8 depend on patch #6.
> >
> > So if the ata maintainers agreed to merge their patch #1 via scsi, and
> > Geert agrees to patch #5 and that it's also merged via scsi, patches #1,
> 
> s/5/6/?

Yes, indeed. And I tried so hard to get all the numbers right :-\

Best regards
Uwe

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