[PATCH] coresight: do not use the BIT() macro in the UAPI header

[PATCH] coresight: do not use the BIT() macro in the UAPI header

[Eugene Syromiatnikov]

The BIT() macro definition is not available for the UAPI headers
(moreover, it can be defined differently in the user space); replace
its usage with the _BITUL() macro that is defined in <linux/const.h>.

Fixes: 237483aa5cf4 ("coresight: stm: adding driver for CoreSight STM component")
Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
---
 include/uapi/linux/coresight-stm.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/coresight-stm.h b/include/uapi/linux/coresight-stm.h
index aac550a..8847dbf 100644
--- a/include/uapi/linux/coresight-stm.h
+++ b/include/uapi/linux/coresight-stm.h
@@ -2,8 +2,10 @@
 #ifndef __UAPI_CORESIGHT_STM_H_
 #define __UAPI_CORESIGHT_STM_H_
 
-#define STM_FLAG_TIMESTAMPED   BIT(3)
-#define STM_FLAG_GUARANTEED    BIT(7)
+#include <linux/const.h>
+
+#define STM_FLAG_TIMESTAMPED   _BITUL(3)
+#define STM_FLAG_GUARANTEED    _BITUL(7)
 
 /*
  * The CoreSight STM supports guaranteed and invariant timing
-- 
2.1.4


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Re: [PATCH] coresight: do not use the BIT() macro in the UAPI header

[Greg Kroah-Hartman]

On Tue, Mar 24, 2020 at 05:22:13AM +0100, Eugene Syromiatnikov wrote:
> The BIT() macro definition is not available for the UAPI headers
> (moreover, it can be defined differently in the user space); replace
> its usage with the _BITUL() macro that is defined in <linux/const.h>.

Why is somehow _BITUL() ok to use here instead?

Just open-code it, I didn't think we could use any BIT()-like macros in
uapi .h files.

thanks,

greg k-h

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Re: [PATCH] coresight: do not use the BIT() macro in the UAPI header

[Eugene Syromiatnikov]

On Tue, Mar 24, 2020 at 07:28:53AM +0100, Greg Kroah-Hartman wrote:
> On Tue, Mar 24, 2020 at 05:22:13AM +0100, Eugene Syromiatnikov wrote:
> > The BIT() macro definition is not available for the UAPI headers
> > (moreover, it can be defined differently in the user space); replace
> > its usage with the _BITUL() macro that is defined in <linux/const.h>.
> 
> Why is somehow _BITUL() ok to use here instead?

It is provided in an UAPI header (include/uapi/linux/const.h)
and is appropriately prefixed with an underscore to avoid conflicts.

> Just open-code it, I didn't think we could use any BIT()-like macros in
> uapi .h files.
> 
> thanks,
> 
> greg k-h
> 


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Re: [PATCH] coresight: do not use the BIT() macro in the UAPI header

[Greg Kroah-Hartman]

On Tue, Mar 24, 2020 at 10:53:04AM +0100, Eugene Syromiatnikov wrote:
> On Tue, Mar 24, 2020 at 07:28:53AM +0100, Greg Kroah-Hartman wrote:
> > On Tue, Mar 24, 2020 at 05:22:13AM +0100, Eugene Syromiatnikov wrote:
> > > The BIT() macro definition is not available for the UAPI headers
> > > (moreover, it can be defined differently in the user space); replace
> > > its usage with the _BITUL() macro that is defined in <linux/const.h>.
> > 
> > Why is somehow _BITUL() ok to use here instead?
> 
> It is provided in an UAPI header (include/uapi/linux/const.h)
> and is appropriately prefixed with an underscore to avoid conflicts.

Because no one uses _ in their own macros?  :)

Anyway, this is fine, but if it's really the way forward, I think a lot
of files will end up being changed...

thanks,

greg k-h

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Re: [PATCH] coresight: do not use the BIT() macro in the UAPI header

[Eugene Syromiatnikov]

On Tue, Mar 24, 2020 at 11:19:38AM +0100, Greg Kroah-Hartman wrote:
> On Tue, Mar 24, 2020 at 10:53:04AM +0100, Eugene Syromiatnikov wrote:
> > On Tue, Mar 24, 2020 at 07:28:53AM +0100, Greg Kroah-Hartman wrote:
> > > On Tue, Mar 24, 2020 at 05:22:13AM +0100, Eugene Syromiatnikov wrote:
> > > > The BIT() macro definition is not available for the UAPI headers
> > > > (moreover, it can be defined differently in the user space); replace
> > > > its usage with the _BITUL() macro that is defined in <linux/const.h>.
> > > 
> > > Why is somehow _BITUL() ok to use here instead?
> > 
> > It is provided in an UAPI header (include/uapi/linux/const.h)
> > and is appropriately prefixed with an underscore to avoid conflicts.
> 
> Because no one uses _ in their own macros?  :)

Well, it is a reserved prefix (ANSI C99, 4.1.2 "Standard headers": "All
other identifiers that begin with an underscore and either an upper-case
letter or another underscore are reserved"), so valid C files shouldn't
use them.

> Anyway, this is fine, but if it's really the way forward, I think a lot
> of files will end up being changed...

There are 5 cases for using BIT() in UAPI headers so far (rtc.h[1],
serio.h[2], psci.h[3], pkt_sched.h[4], coresight-stm.h), two of them were
conversions from the open-coded variant; the usage of _BITUL in pkt_sched.h
made me think that it is the better approach since people tend to use
BIT-like macro anyway, so, by increasing a number of cases it may raise
awareness of the UAPI specifics.

[1] https://lore.kernel.org/lkml/20200324041209.GA30727@asgard.redhat.com/
[2] https://lore.kernel.org/lkml/20200324041341.GA32335@asgard.redhat.com/
[3] https://lore.kernel.org/lkml/20200324041526.GA1978@asgard.redhat.com/
[4] https://lore.kernel.org/lkml/20200324041920.GA7068@asgard.redhat.com/

> 
> thanks,
> 
> greg k-h
> 


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Re: [PATCH] coresight: do not use the BIT() macro in the UAPI header

[Mathieu Poirier]

On Mon, 23 Mar 2020 at 22:22, Eugene Syromiatnikov <esyr@redhat.com> wrote:
>
> The BIT() macro definition is not available for the UAPI headers
> (moreover, it can be defined differently in the user space); replace
> its usage with the _BITUL() macro that is defined in <linux/const.h>.
>
> Fixes: 237483aa5cf4 ("coresight: stm: adding driver for CoreSight STM component")
> Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
> ---
>  include/uapi/linux/coresight-stm.h | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/include/uapi/linux/coresight-stm.h b/include/uapi/linux/coresight-stm.h
> index aac550a..8847dbf 100644
> --- a/include/uapi/linux/coresight-stm.h
> +++ b/include/uapi/linux/coresight-stm.h
> @@ -2,8 +2,10 @@
>  #ifndef __UAPI_CORESIGHT_STM_H_
>  #define __UAPI_CORESIGHT_STM_H_
>
> -#define STM_FLAG_TIMESTAMPED   BIT(3)
> -#define STM_FLAG_GUARANTEED    BIT(7)
> +#include <linux/const.h>
> +
> +#define STM_FLAG_TIMESTAMPED   _BITUL(3)
> +#define STM_FLAG_GUARANTEED    _BITUL(7)

Greg, if you want to pick this up right away:

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>

Otherwise let me know and I'll add it to my next tree.

Thanks,
Mathieu

>
>  /*
>   * The CoreSight STM supports guaranteed and invariant timing
> --
> 2.1.4
>

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Re: [PATCH] coresight: do not use the BIT() macro in the UAPI header

[Greg Kroah-Hartman]

On Tue, Mar 24, 2020 at 09:31:15AM -0600, Mathieu Poirier wrote:
> On Mon, 23 Mar 2020 at 22:22, Eugene Syromiatnikov <esyr@redhat.com> wrote:
> >
> > The BIT() macro definition is not available for the UAPI headers
> > (moreover, it can be defined differently in the user space); replace
> > its usage with the _BITUL() macro that is defined in <linux/const.h>.
> >
> > Fixes: 237483aa5cf4 ("coresight: stm: adding driver for CoreSight STM component")
> > Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
> > ---
> >  include/uapi/linux/coresight-stm.h | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/uapi/linux/coresight-stm.h b/include/uapi/linux/coresight-stm.h
> > index aac550a..8847dbf 100644
> > --- a/include/uapi/linux/coresight-stm.h
> > +++ b/include/uapi/linux/coresight-stm.h
> > @@ -2,8 +2,10 @@
> >  #ifndef __UAPI_CORESIGHT_STM_H_
> >  #define __UAPI_CORESIGHT_STM_H_
> >
> > -#define STM_FLAG_TIMESTAMPED   BIT(3)
> > -#define STM_FLAG_GUARANTEED    BIT(7)
> > +#include <linux/const.h>
> > +
> > +#define STM_FLAG_TIMESTAMPED   _BITUL(3)
> > +#define STM_FLAG_GUARANTEED    _BITUL(7)
> 
> Greg, if you want to pick this up right away:
> 
> Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> 
> Otherwise let me know and I'll add it to my next tree.

I'll take it now, thanks.

greg k-h

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