From: Finn Thain <fthain@telegraphics.com.au>
To: Arnd Bergmann <arnd@arndb.de>
Cc: LEROY Christophe <christophe.leroy@c-s.fr>,
Linux Fbdev development list <linux-fbdev@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
linux-m68k <linux-m68k@lists.linux-m68k.org>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Paul Mackerras <paulus@samba.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH v8 20/25] powerpc, fbdev: Use arch_nvram_ops methods instead of nvram_read_byte() and nvram_write_byte()
Date: Tue, 1 Jan 2019 12:10:11 +1100 (AEDT) [thread overview]
Message-ID: <alpine.LNX.2.21.1901011154590.574@nippy.intranet> (raw)
In-Reply-To: <CAK8P3a3645im4aFDi2mNjwcCe=jvmDLkKK_ZSwG1POOLUq=+QQ@mail.gmail.com>
On Mon, 31 Dec 2018, Arnd Bergmann wrote:
> On Sun, Dec 30, 2018 at 12:43 AM Finn Thain <fthain@telegraphics.com.au> wrote:
>
> >
> > Is there some benefit, or is that just personal taste?
> >
> > Avoiding changes to call sites avoids code review, but I think 1) the
> > thinkpad_acpi changes have already been reviewed and 2) the fbdev changes
> > need review anyway.
> >
> > Your suggesion would add several new entities and one extra layer of
> > indirection.
> >
> > I think indirection harms readability because now the reader now has to go
> > and look up the meaning of the new entities.
> >
> > It's not the case that we need to choose between definitions of
> > nvram_read_byte() at compile time, or stub them out:
> >
> > #ifdef CONFIG_FOO
> > static inline unsigned char nvram_read_byte(int addr)
> > {
> > return arch_nvram_ops.read_byte(addr);
> > }
> > #else
> > static inline unsigned char nvram_read_byte(int addr) { }
> > #endif
> >
> > And I don't anticipate a need for a macro here either:
> >
> > #define nvram_read_byte(a) random_nvram_read_byte_impl(a)
> >
> > I think I've used the simplest solution.
>
> Having the indirection would help if the inline function can
> encapsulate the NULL pointer check, like
>
> static inline unsigned char nvram_read_byte(loff_t addr)
> {
> char data;
>
> if (!IS_ENABLED(CONFIG_NVRAM))
> return 0xff;
>
> if (arch_nvram_ops.read_byte)
> return arch_nvram_ops.read_byte(addr);
>
> if (arch_nvram_ops.read)
> return arch_nvram_ops.read(char, 1, &addr);
>
> return 0xff;
> }
>
The semantics of .read_byte and .read are subtly different. For CONFIG_X86
and CONFIG_ATARI, .read implies checksum validation and .read_byte does
not.
In particular, in the thinkpad_acpi case, checksum validation isn't used,
but in the atari_scsi case, it is.
So I like to see drivers explicitly call the method they want. I didn't
want to obscure this distinction in a helper.
--
next prev parent reply other threads:[~2019-01-01 1:10 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-26 0:37 [PATCH v8 00/25] Re-use nvram module Finn Thain
2018-12-26 0:37 ` [PATCH v8 24/25] powerpc: Adopt nvram module for PPC64 Finn Thain
2018-12-29 22:36 ` Arnd Bergmann
2018-12-30 3:28 ` Finn Thain
2018-12-31 12:32 ` Arnd Bergmann
2019-01-01 1:38 ` Finn Thain
2019-01-04 8:45 ` Finn Thain
2019-01-06 23:36 ` Michael Ellerman
2019-01-07 4:52 ` Finn Thain
2019-01-08 9:27 ` Michael Ellerman
2019-01-08 22:51 ` Finn Thain
2018-12-26 0:37 ` [PATCH v8 07/25] char/nvram: Allow the set_checksum and initialize ioctls to be omitted Finn Thain
2018-12-26 0:37 ` [PATCH v8 22/25] powerpc: Remove CONFIG_GENERIC_NVRAM and adopt CONFIG_HAVE_ARCH_NVRAM_OPS Finn Thain
2019-01-03 8:05 ` Christoph Hellwig
2019-01-03 22:11 ` Finn Thain
2018-12-26 0:37 ` [PATCH v8 16/25] powerpc: Add missing ppc_md.nvram_size for CHRP and PowerMac Finn Thain
2018-12-26 0:37 ` [PATCH v8 03/25] m68k/atari: Replace nvram_{read,write}_byte with arch_nvram_ops Finn Thain
2018-12-26 0:37 ` [PATCH v8 11/25] m68k/mac: Use macros for RTC accesses not magic numbers Finn Thain
2018-12-26 0:37 ` [PATCH v8 02/25] m68k/atari: Move Atari-specific code out of drivers/char/nvram.c Finn Thain
2018-12-28 16:51 ` LEROY Christophe
2018-12-29 1:16 ` Finn Thain
2019-01-02 22:29 ` Finn Thain
2018-12-26 0:37 ` [PATCH v8 21/25] nvram: Drop nvram_* symbol exports and prototypes Finn Thain
2018-12-26 0:37 ` [PATCH v8 14/25] char/nvram: Add "devname:nvram" module alias Finn Thain
2018-12-26 0:37 ` [PATCH v8 08/25] char/nvram: Implement NVRAM read/write methods Finn Thain
2018-12-26 0:37 ` [PATCH v8 15/25] powerpc: Clean up nvram includes Finn Thain
2018-12-26 0:37 ` [PATCH v8 05/25] char/nvram: Adopt arch_nvram_ops Finn Thain
2019-01-03 8:02 ` Christoph Hellwig
2019-01-03 22:08 ` Finn Thain
2019-01-04 17:56 ` Christoph Hellwig
2019-01-04 22:05 ` Finn Thain
2018-12-26 0:37 ` [PATCH v8 25/25] powerpc: Remove pmac_xpram_{read,write} functions Finn Thain
2018-12-26 0:37 ` [PATCH v8 06/25] x86/thinkpad_acpi: Use arch_nvram_ops methods instead of nvram_read_byte() and nvram_write_byte() Finn Thain
2018-12-26 0:37 ` [PATCH v8 12/25] m68k/mac: Fix PRAM accessors Finn Thain
2018-12-26 0:37 ` [PATCH v8 18/25] powerpc: Implement nvram sync ioctl Finn Thain
2018-12-29 22:19 ` Arnd Bergmann
2018-12-30 7:25 ` Finn Thain
2018-12-30 23:13 ` Finn Thain
2018-12-31 12:17 ` Arnd Bergmann
2018-12-31 12:16 ` Arnd Bergmann
2019-01-01 1:06 ` Finn Thain
2019-01-02 22:25 ` Finn Thain
2018-12-26 0:37 ` [PATCH v8 23/25] char/generic_nvram: Remove as unused Finn Thain
2018-12-26 0:37 ` [PATCH v8 10/25] m68k/mac: Adopt naming and calling conventions for PRAM routines Finn Thain
2018-12-26 0:37 ` [PATCH v8 09/25] m68k/atari: Implement arch_nvram_ops methods and enable CONFIG_HAVE_ARCH_NVRAM_OPS Finn Thain
2018-12-26 0:37 ` [PATCH v8 17/25] powerpc: Implement arch_nvram_ops.get_size() and remove old nvram_* exports Finn Thain
2018-12-26 0:37 ` [PATCH v8 04/25] char/nvram: Re-order functions to remove forward declarations and #ifdefs Finn Thain
2018-12-26 0:37 ` [PATCH v8 13/25] m68k: Dispatch nvram_ops calls to Atari or Mac functions Finn Thain
2018-12-29 22:27 ` Arnd Bergmann
2018-12-30 7:26 ` Finn Thain
2018-12-30 17:53 ` LEROY Christophe
2018-12-30 22:12 ` Finn Thain
2018-12-31 12:19 ` Arnd Bergmann
2018-12-26 0:37 ` [PATCH v8 19/25] powerpc, fbdev: Use NV_CMODE and NV_VMODE only when CONFIG_PPC32 && CONFIG_PPC_PMAC && CONFIG_NVRAM Finn Thain
2018-12-26 0:37 ` [PATCH v8 20/25] powerpc, fbdev: Use arch_nvram_ops methods instead of nvram_read_byte() and nvram_write_byte() Finn Thain
2018-12-29 17:02 ` LEROY Christophe
2018-12-29 23:43 ` Finn Thain
2018-12-31 12:29 ` Arnd Bergmann
2019-01-01 1:10 ` Finn Thain [this message]
2019-01-05 23:06 ` Finn Thain
2018-12-26 0:37 ` [PATCH v8 01/25] scsi/atari_scsi: Don't select CONFIG_NVRAM Finn Thain
2018-12-28 16:38 ` LEROY Christophe
2018-12-29 1:06 ` Finn Thain
2018-12-29 1:33 ` Michael Schmitz
2018-12-29 2:34 ` Finn Thain
2018-12-29 2:50 ` Michael Schmitz
2018-12-29 21:37 ` Arnd Bergmann
2018-12-30 17:50 ` LEROY Christophe
2018-12-30 18:06 ` James Bottomley
2018-12-30 21:44 ` Finn Thain
2018-12-30 22:45 ` Finn Thain
2018-12-29 16:55 ` LEROY Christophe
2018-12-29 18:54 ` Michael Schmitz
2018-12-29 2:54 ` Michael Schmitz
2018-12-29 22:45 ` [PATCH v8 00/25] Re-use nvram module Arnd Bergmann
2018-12-30 0:09 ` Finn Thain
2018-12-30 4:05 ` Finn Thain
2018-12-31 12:22 ` Arnd Bergmann
2018-12-31 22:54 ` Finn Thain
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