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Date: Tue, 22 Oct 2019 13:35:27 -0400 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: Joe Perches <joe@...ches.com> Cc: Geert Uytterhoeven <geert@...ux-m68k.org>, Ludovic Desroches <ludovic.desroches@...rochip.com>, Ulf Hansson <ulf.hansson@...aro.org>, Nicolas Ferre <nicolas.ferre@...rochip.com>, Alexandre Belloni <alexandre.belloni@...tlin.com>, Jaehoon Chung <jh80.chung@...sung.com>, "David S . Miller" <davem@...emloft.net>, "Rafael J . Wysocki" <rafael@...nel.org>, Johannes Berg <johannes@...solutions.net>, Linux MMC List <linux-mmc@...r.kernel.org>, Linux ARM <linux-arm-kernel@...ts.infradead.org>, netdev <netdev@...r.kernel.org>, linux-wireless <linux-wireless@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 1/7] debugfs: Add debugfs_create_xul() for hexadecimal unsigned long On Tue, Oct 22, 2019 at 02:07:34AM -0700, Joe Perches wrote: > On Tue, 2019-10-22 at 10:03 +0200, Geert Uytterhoeven wrote: > > Hi Joe, > > Hey again Geert. > > > On Mon, Oct 21, 2019 at 5:37 PM Joe Perches <joe@...ches.com> wrote: > > > On Mon, 2019-10-21 at 16:37 +0200, Geert Uytterhoeven wrote: > > > > The existing debugfs_create_ulong() function supports objects of > > > > type "unsigned long", which are 32-bit or 64-bit depending on the > > > > platform, in decimal form. To format objects in hexadecimal, various > > > > debugfs_create_x*() functions exist, but all of them take fixed-size > > > > types. > > > > > > > > Add a debugfs helper for "unsigned long" objects in hexadecimal format. > > > > This avoids the need for users to open-code the same, or introduce > > > > bugs when casting the value pointer to "u32 *" or "u64 *" to call > > > > debugfs_create_x{32,64}(). > > > [] > > > > diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h > > > [] > > > > @@ -356,4 +356,14 @@ static inline ssize_t debugfs_write_file_bool(struct file *file, > > > > > > > > #endif > > > > > > > > +static inline void debugfs_create_xul(const char *name, umode_t mode, > > > > + struct dentry *parent, > > > > + unsigned long *value) > > > > +{ > > > > + if (sizeof(*value) == sizeof(u32)) > > > > + debugfs_create_x32(name, mode, parent, (u32 *)value); > > > > + else > > > > + debugfs_create_x64(name, mode, parent, (u64 *)value); > > > > > > trivia: the casts are unnecessary. > > > > They are necessary, in both calls (so using #ifdef as suggested below > > won't help): > > Silly thinko, (I somehow thought the compiler would > eliminate the code after the branch not taken, but > of course it has to compile it first... oops) > though the #ifdef should work. > > > > This might be more sensible using #ifdef > > > > > > static inline void debugfs_create_xul(const char *name, umode_t mode, > > > struct dentry *parent, > > > unsigned long *value) > > > { > > > #if BITS_PER_LONG == 64 > > > debugfs_create_x64(name, mode, parent, value); > > > #else > > > debugfs_create_x32(name, mode, parent, value); > > > #endif > > > } > > > > ... at the expense of the compiler checking only one branch. > > > > Just like "if (IS_ENABLED(CONFIG_<foo>)" (when possible) is preferred > > over "#ifdef CONFIG_<foo>" because of compile-coverage, I think using > > "if" here is better than using "#if". > > True if all compilers will always eliminate the unused branch. Good ones will, we don't care about bad ones :)
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