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From: Guenter Roeck <linux@roeck-us.net>
To: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Matthias Maennich <maennich@google.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"Cc: Android Kernel" <kernel-team@android.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jessica Yu <jeyu@kernel.org>,
	"Joel Fernandes (Google)" <joel@joelfernandes.org>,
	Lucas De Marchi <lucas.de.marchi@gmail.com>,
	maco@android.com, sspatil@google.com,
	Will Deacon <will@kernel.org>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	linux-modules@vger.kernel.org,
	linux-usb <linux-usb@vger.kernel.org>,
	usb-storage@lists.one-eyed-alien.net,
	linux-watchdog@vger.kernel.org
Subject: Re: [PATCH v4 12/12] RFC: watchdog: export core symbols in WATCHDOG_CORE namespace
Date: Wed, 4 Sep 2019 05:12:43 -0700
Message-ID: <c6ac941c-06a4-e5dc-5cb9-fca7b40d7e9a@roeck-us.net> (raw)
In-Reply-To: <CAK7LNARYqqCSCc0G4FL7_bj80iMoLLJrUJ7B3+huD25EUkrttA@mail.gmail.com>

On 9/4/19 1:45 AM, Masahiro Yamada wrote:
> On Wed, Sep 4, 2019 at 1:10 AM Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> On Tue, Sep 03, 2019 at 04:06:38PM +0100, Matthias Maennich wrote:
>>> Modules using symbols from the WATCHDOG_CORE namespace are required to
>>> explicitly import the namespace. This patch was generated with the
>>> following steps and serves as a reference to use the symbol namespace
>>> feature:
>>>
>>>   1) Use EXPORT_SYMBOL_NS* macros instead of EXPORT_SYMBOL* for symbols
>>>      in watchdog_core.c
>>>   2) make  (see warnings during modpost about missing imports)
>>>   3) make nsdeps
>>>
>>> I used 'allmodconfig' for the above steps to ensure all occurrences are
>>> patched.
>>>
>>> Defining DEFAULT_SYMBOL_NAMESPACE in the Makefile is not trivial in this
>>> case as not only watchdog_core is defined in drivers/watchdog/Makefile.
>>> Hence this patch uses the variant of using the EXPORT_SYMBOL_NS* macros
>>> to export into a different namespace.
>>>
>>> An alternative to this patch would be a single definition line before
>>> any use of EXPORT_SYMBOL*:
>>>   #define DEFAULT_SYMBOL_NAMESPACE WATCHDOG_CORE
>>>
>>> This patch serves as a reference on how to use the symbol namespaces.
>>>
>>> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Signed-off-by: Matthias Maennich <maennich@google.com>
>>
>> As mentioned before, I am opposed to this set of changes. I don't see
>> the point of restricting the use of exported symbols in WATCHDOG_CORE.
>>
>> Guenter
> 
> 
> I agree.
> 
> I do not like this patch set either.
> 

Note that I don't object to the patch set in general. There may be symbols
which only need be exported in the context of a single subsystem or even
driver (if a driver consists of more than one module). For example, a mfd
driver may export symbols which should only be called by its client drivers.
In such a situation, it may well be beneficial to limit the use of exported
symbols.

I am not sure what good that does in practice (if I understand correctly,
a driver only has to declare that it wants to use a restricted use symbol
if it wants to use it), but that is a different question.

Guenter

  reply index

Thread overview: 105+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20180716122125.175792-1-maco@android.com>
2019-08-13 12:16 ` [PATCH v2 0/10] Symbol namespaces - RFC Matthias Maennich
2019-08-13 12:16   ` [PATCH v2 01/10] module: support reading multiple values per modinfo tag Matthias Maennich
2019-08-13 12:40     ` Greg KH
2019-08-13 12:16   ` [PATCH v2 02/10] export: explicitly align struct kernel_symbol Matthias Maennich
2019-08-13 12:41     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 03/10] module: add support for symbol namespaces Matthias Maennich
2019-08-13 15:26     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 04/10] modpost: " Matthias Maennich
2019-08-13 15:27     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 05/10] module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS Matthias Maennich
2019-08-13 18:17     ` Greg KH
2019-08-13 20:15     ` Saravana Kannan
2019-08-14 12:54       ` Matthias Maennich
2019-08-14 17:34         ` Saravana Kannan
2019-08-13 12:17   ` [PATCH v2 06/10] export: allow definition default namespaces in Makefiles or sources Matthias Maennich
2019-08-13 18:16     ` Greg KH
2019-08-13 18:16     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 07/10] modpost: add support for generating namespace dependencies Matthias Maennich
2019-08-13 18:21     ` Greg KH
2019-08-13 12:17   ` [PATCH v2 08/10] scripts: Coccinelle script for " Matthias Maennich
2019-08-13 12:31     ` Julia Lawall
2019-08-13 12:44     ` Greg KH
2019-08-14  6:36     ` [Cocci] " Himanshu Jha
2019-08-14  8:03       ` Matthias Maennich
2019-08-14 12:00     ` [v2 " Markus Elfring
2019-08-15 13:50     ` Markus Elfring
2019-08-22  9:18       ` Matthias Maennich
2019-08-22 11:00         ` Markus Elfring
2019-08-13 12:17   ` [PATCH v2 09/10] usb-storage: remove single-use define for debugging Matthias Maennich
2019-08-13 12:42     ` Greg KH
2019-08-13 13:12       ` Greg KH
2019-08-13 12:17   ` [PATCH v2 10/10] RFC: usb-storage: export symbols in USB_STORAGE namespace Matthias Maennich
2019-08-13 12:45     ` Greg KH
2019-08-13 12:47     ` Greg KH
2019-08-13 15:02       ` Matthias Maennich
     [not found]   ` <20190821114955.12788-1-maennich@google.com>
2019-08-21 11:49     ` [PATCH v3 01/11] module: support reading multiple values per modinfo tag Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 02/11] export: explicitly align struct kernel_symbol Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 03/11] module: add support for symbol namespaces Matthias Maennich
2019-08-27 15:37       ` Jessica Yu
2019-08-27 16:04         ` Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 04/11] modpost: " Matthias Maennich
2019-08-26 16:21       ` Jessica Yu
2019-08-27 14:41         ` Matthias Maennich
2019-08-28  9:43           ` Jessica Yu
2019-08-28  9:55             ` Matthias Maennich
2019-08-28 10:16               ` Jessica Yu
2019-08-21 11:49     ` [PATCH v3 05/11] module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 06/11] export: allow definition default namespaces in Makefiles or sources Matthias Maennich
2019-08-28 10:49       ` Jessica Yu
2019-08-28 10:56         ` Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 07/11] modpost: add support for generating namespace dependencies Matthias Maennich
2019-08-21 11:49     ` [PATCH v3 08/11] scripts: Coccinelle script for " Matthias Maennich
2019-08-22  6:09       ` [v3 " Markus Elfring
2019-08-29 12:13       ` [PATCH v3 " Jessica Yu
2019-08-21 11:49     ` [PATCH v3 09/11] usb-storage: remove single-use define for debugging Matthias Maennich
2019-08-21 12:37       ` Greg KH
2019-08-21 13:21       ` Thomas Gleixner
2019-08-21 13:32         ` Greg KH
2019-08-21 11:49     ` [PATCH v3 10/11] RFC: usb-storage: export symbols in USB_STORAGE namespace Matthias Maennich
2019-08-21 12:38       ` Greg KH
2019-08-21 14:36         ` Jessica Yu
2019-08-21 23:13       ` Christoph Hellwig
2019-08-22  8:32         ` Matthias Maennich
2019-09-03 15:06 ` [PATCH v4 00/12] Symbol Namespaces Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 01/12] module: support reading multiple values per modinfo tag Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 02/12] export: explicitly align struct kernel_symbol Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 03/12] module: add support for symbol namespaces Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 04/12] modpost: " Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 05/12] module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 06/12] export: allow definition default namespaces in Makefiles or sources Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 07/12] modpost: add support for generating namespace dependencies Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 08/12] scripts: Coccinelle script for " Matthias Maennich
2019-09-04  9:53     ` Masahiro Yamada
2019-09-05 14:46       ` Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 09/12] docs: Add documentation for Symbol Namespaces Matthias Maennich
2019-09-04  7:16     ` Greg KH
2019-09-03 15:06   ` [PATCH v4 10/12] usb-storage: remove single-use define for debugging Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 11/12] RFC: usb-storage: export symbols in USB_STORAGE namespace Matthias Maennich
2019-09-03 15:06   ` [PATCH v4 12/12] RFC: watchdog: export core symbols in WATCHDOG_CORE namespace Matthias Maennich
2019-09-03 16:10     ` Guenter Roeck
2019-09-04  8:45       ` Masahiro Yamada
2019-09-04 12:12         ` Guenter Roeck [this message]
2019-09-04 16:16           ` [usb-storage] " Matthew Dharm
2019-09-05 10:41             ` Jessica Yu
2019-09-05 10:52               ` Arnd Bergmann
2019-09-05 11:16                 ` Jessica Yu
2019-09-05 11:25                   ` Masahiro Yamada
2019-09-05 12:00                     ` Greg Kroah-Hartman
2019-09-05 11:25               ` Matthias Maennich
2019-09-04  9:37   ` [PATCH v4 00/12] Symbol Namespaces Masahiro Yamada
2019-09-06 10:32 ` [PATCH v5 00/11] " Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 01/11] module: support reading multiple values per modinfo tag Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 02/11] export: explicitly align struct kernel_symbol Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 03/11] module: add support for symbol namespaces Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 04/11] modpost: " Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 05/11] module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 06/11] export: allow definition default namespaces in Makefiles or sources Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 07/11] modpost: add support for generating namespace dependencies Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 08/11] scripts: Coccinelle script for " Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 09/11] docs: Add documentation for Symbol Namespaces Matthias Maennich
2019-09-06 10:32   ` [PATCH v5 10/11] usb-storage: remove single-use define for debugging Matthias Maennich
2019-09-06 12:59     ` Jessica Yu
2019-09-06 13:22       ` Greg KH
2019-09-06 10:32   ` [PATCH v5 11/11] usb-storage: export symbols in USB_STORAGE namespace Matthias Maennich
2019-09-09  8:35   ` [PATCH v5 00/11] Symbol Namespaces Jessica Yu

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