Re: [PATCH v1 0/2] firewire: Simplify storing pointers in device id struct

[Takashi Sakamoto <o-takashi@sakamocchi.jp>]

Hi,

Thanks for the patches. As far as I can see, they can be applied neither
any compilation failures and running regressions.

We are in the middle of merge window for v7.2. I had not planned to send any
changes to upstream for firewire subsystem, but there is still some time
before it closes. If the sound subsystem maintainer does not mind, I
would like to proceed.

Just out of curiosity, what does the CHERI extension adopted to RISC-V
architecture require in terms of kernel programming? Is taking extra
care when storing pointer values in long-type variables sufficient in
driver code?


Thanks

Takashi Sakamoto

On Sun, Apr 19, 2026 at 08:42:12AM +0200, Uwe Kleine-König (The Capable Hub) wrote:
> Hello,
> 
> <linux/mod_devicetable.h> contains several device_id structs for various
> device types.
> 
> Most of them have one of:
> 
>  - kernel_ulong_t driver_data (sometimes called "driver_info", sometimes 
>    the type is plain unsigned long)
>  - const void *data (sometimes called "driver_data" or "context", sometimes not const)
> 
> A considerable amount of drivers for the first category uses the
> unsigned long variable to store a pointer. This involves casting both
> for assignment and usage.
> 
> An additional complication exists for the CHERI hardware extension
> where sizeof(void *) > sizeof(unsigned long). So with that an unsigned
> long variable cannot be used to store a pointer.
> 
> To address both issues this series replaces the unsigned long variable
> by an anonymous union containing both an unsigned long and a pointer.
> 
> For all non-CHERI architectures this isn't an ABI change because all
> have sizeof(void *) == sizeof(unsigned long).
> 
> The first patch changes the definition of struct ieee1394_device_id. The
> second drops some casts in sound drivers. (There are no other firewire
> drivers that could benefit.) I adapted all sound drivers in a single
> patch, tell me if I should split per driver.
> 
> For merging I suggest to take the whole series via the ALSA tree in the
> next merge window, as there are no modified files that are specific to
> firewire only and the second patch depends on the first.
> 
> Best regards
> Uwe
> 
> Uwe Kleine-König (The Capable Hub) (2):
>   firewire: Simplify storing pointers in device id struct
>   ALSA: firewire: Make use of ieee1394's .driver_data_ptr
> 
>  include/linux/mod_devicetable.h |  5 ++++-
>  sound/firewire/dice/dice.c      | 34 ++++++++++++++++-----------------
>  sound/firewire/fireface/ff.c    | 12 ++++++------
>  sound/firewire/motu/motu.c      |  6 +++---
>  sound/firewire/oxfw/oxfw.c      |  4 ++--
>  5 files changed, 32 insertions(+), 29 deletions(-)
> 
> 
> base-commit: 028ef9c96e96197026887c0f092424679298aae8
> -- 
> 2.47.3
>