Re: [PATCH] firmware_loader: change enum fw_opt to u32 - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: Scott Branden <scott.branden@broadcom.com>,
	David Brown <david.brown@linaro.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Shuah Khan <shuah@kernel.org>,
	bjorn.andersson@linaro.org,
	Shuah Khan <skhan@linuxfoundation.org>,
	Arnd Bergmann <arnd@arndb.de>,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	linux-fsdevel@vger.kernel.org,
	BCM Kernel Feedback <bcm-kernel-feedback-list@broadcom.com>,
	Olof Johansson <olof@lixom.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Colin Ian King <colin.king@canonical.com>,
	Kees Cook <keescook@chromium.org>, Takashi Iwai <tiwai@suse.de>,
	linux-kselftest@vger.kernel.org, Andy Gross <agross@kernel.org>
Subject: Re: [PATCH] firmware_loader: change enum fw_opt to u32
Date: Sat, 23 May 2020 08:05:48 +0200	[thread overview]
Message-ID: <20200523060548.GA3124611@kroah.com> (raw)
In-Reply-To: <20200522230025.GG11244@42.do-not-panic.com>

On Fri, May 22, 2020 at 11:00:25PM +0000, Luis Chamberlain wrote:
> On Fri, May 22, 2020 at 03:49:05PM -0700, Scott Branden wrote:
> > Hi Luis,
> > 
> > On 2020-05-22 3:45 p.m., Luis Chamberlain wrote:
> > > On Fri, May 22, 2020 at 02:46:58PM -0700, Scott Branden wrote:
> > > >   /**
> > > > - * enum fw_opt - options to control firmware loading behaviour
> > > > + * fw_opt - options to control firmware loading behaviour
> > > >    *
> > > >    * @FW_OPT_UEVENT: Enables the fallback mechanism to send a kobject uevent
> > > >    *	when the firmware is not found. Userspace is in charge to load the
> > > > @@ -33,15 +33,13 @@
> > > >    *	the platform's main firmware. If both this fallback and the sysfs
> > > >    *      fallback are enabled, then this fallback will be tried first.
> > > >    */
> > > > -enum fw_opt {
> > > > -	FW_OPT_UEVENT			= BIT(0),
> > > > -	FW_OPT_NOWAIT			= BIT(1),
> > > > -	FW_OPT_USERHELPER		= BIT(2),
> > > > -	FW_OPT_NO_WARN			= BIT(3),
> > > > -	FW_OPT_NOCACHE			= BIT(4),
> > > > -	FW_OPT_NOFALLBACK_SYSFS		= BIT(5),
> > > > -	FW_OPT_FALLBACK_PLATFORM	= BIT(6),
> > > > -};
> > > > +#define FW_OPT_UEVENT			BIT(0)
> > > > +#define FW_OPT_NOWAIT			BIT(1)
> > > > +#define FW_OPT_USERHELPER		BIT(2)
> > > > +#define FW_OPT_NO_WARN			BIT(3)
> > > > +#define FW_OPT_NOCACHE			BIT(4)
> > > > +#define FW_OPT_NOFALLBACK_SYSFS		BIT(5)
> > > > +#define FW_OPT_FALLBACK_PLATFORM	BIT(6)
> > > Everything looked good up to here. The enum defines each flag.
> > > We just want to use an enum for *one* flag represetnation, not
> > > a bundle.
> >
> > I do not know exactly what you are looking for then.  The FW_OPT_*
> > values are OR'd together in the code.  You still want the fw_opt enum
> > above left in place entirely and then the values used in OR'd
> > together?
> 
> Yes, exactly. If they are combined then we just use a u32 to represent
> these are then flags combined. An enum represents just *one* flag, not
> a set which are OR'd together. Let me know if this is still not clear.

If this is the case, why have an enum at all?  What difference is it
from a #define like was done here?

thanks,

greg k-h