Re: [PATCH v5] scsi/ata: Use unsigned int for cmd's type in ioctls in scsi_host_template

[Nathan Chancellor <natechancellor@gmail.com>]

On Fri, Feb 08, 2019 at 12:05:01AM -0800, Christoph Hellwig wrote:
> On Thu, Feb 07, 2019 at 09:07:20AM -0700, Nathan Chancellor wrote:
> > Clang warns several times in the scsi subsystem (trimmed for brevity):
> > 
> > drivers/scsi/hpsa.c:6209:7: warning: overflow converting case value to
> > switch condition type (2147762695 to 18446744071562347015) [-Wswitch]
> >         case CCISS_GETBUSTYPES:
> >              ^
> > drivers/scsi/hpsa.c:6208:7: warning: overflow converting case value to
> > switch condition type (2147762694 to 18446744071562347014) [-Wswitch]
> >         case CCISS_GETHEARTBEAT:
> >              ^
> > 
> > The root cause is that the _IOC macro can generate really large numbers,
> > which don't fit into type 'int', which is used for the cmd parameter in
> > the ioctls in scsi_host_template. My research into how GCC and Clang are
> > handling this at a low level didn't prove fruitful. However, looking at
> > the rest of the kernel tree, all ioctls use an 'unsigned int' for the
> > cmd parameter, which will fit all of the _IOC values in the scsi/ata
> > subsystems.
> > 
> > Make that change because none of the ioctls expect a negative value for
> > any command, it brings the ioctls inline with the reset of the kernel,
> > and it removes ambiguity, which is never good when dealing with compilers.
> > 
> > Link: https://github.com/ClangBuiltLinux/linux/issues/85
> > Link: https://github.com/ClangBuiltLinux/linux/issues/154
> > Link: https://github.com/ClangBuiltLinux/linux/issues/157
> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> > Acked-by: Bradley Grove <bgrove@attotech.com>
> > Acked-by: Don Brace <don.brace@microsemi.com>
> > Reviewed-by: Bart Van Assche <bvanassche@acm.org>
> > Tested-by: Nick Desaulniers <ndesaulniers@google.com>
> 
> Looks good:
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Thank you for the review, it is much appreciated!

Nathan