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From:   liaoweixiong <liaoweixiong@allwinnertech.com>
Subject: Re: [RFC v7 2/5] dt-bindings: pstore-block: new support for blkoops
To:     Rob Herring <robh@kernel.org>
Cc:     Kees Cook <keescook@chromium.org>,
        Anton Vorontsov <anton@enomsg.org>,
        Colin Cross <ccross@android.com>,
        Tony Luck <tony.luck@intel.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Mark Rutland <mark.rutland@arm.com>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "David S. Miller" <davem@davemloft.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Nicolas Ferre <nicolas.ferre@microchip.com>,
        Arnd Bergmann <arnd@arndb.de>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org
References: <1548245116-6360-1-git-send-email-liaoweixiong@allwinnertech.com>
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 <20190130160707.GA31844@bogus>
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Date:   Wed, 13 Feb 2019 21:52:02 +0800
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On 2019-01-31 00:07, Rob Herring wrote:> On Wed, Jan 23, 2019 at
08:05:13PM +0800, liaoweixiong wrote:
>> Create DT binding document for blkoops.
>>
>> Signed-off-by: liaoweixiong <liaoweixiong@allwinnertech.com>
>> ---
>>  .../devicetree/bindings/pstore-block/blkoops.txt   | 32 ++++++++++++++++++++++
> 
> /bindings/pstore/...
> 
> I wouldn't call it blkoops either. I believe ramoops is called that to 
> maintain compatibility keeping the same kernel module name that 
> preceeded pstore.
> 

Fixed.

In addition, I don't known whether should we move
ramreserved-memory/ooos.txt to /bindings/pstore. This is for maintainer
to decide, and do it on other patch.

>>  MAINTAINERS                                        |  1 +
>>  2 files changed, 33 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/pstore-block/blkoops.txt
>>
>> diff --git a/Documentation/devicetree/bindings/pstore-block/blkoops.txt b/Documentation/devicetree/bindings/pstore-block/blkoops.txt
>> new file mode 100644
>> index 0000000..a25835b
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/pstore-block/blkoops.txt
>> @@ -0,0 +1,32 @@
>> +Blkoops oops logger
>> +===================
>> +
>> +Blkoops provides a block partition for oops, excluding panics now, so they can
>> +be recovered after a reboot.
>> +
>> +Any space of block partition will be used for a circular buffer of oops records.
>> +These records have a configurable size, with a size of 0 indicating that they
>> +should be disabled.
>> +
>> +"partition-size" and at least one of "dmesg-size" or "pmsg-size" must be set
>> +non-zero, but are otherwise optional as listed below.
>> +
>> +Blkoops will take value from Kconfig if device tree do not set, but settings
>> +from module parameters can also overwrite them.
> 
> That's all kernel details not relevant to the binidng.
> 

Deleted.

>> +
>> +Required properties:
>> +
>> +- compatible: must be "blkoops".
>> +
>> +- partition-size: size in kbytes, must be a multiple of 4.
> 
> This seems unnecessary given a partition has a known size.
> 

partition-size is necessary for psotre/blk. User should tell pstore/blk
how large space can it use.

>> +
>> +Optional properties:
>> +
>> +- partition-path: strings must begin with "/dev", tell blkoops which partition
>> +  it can used. If it is not set, blkoops will drop all data when reboot.
> 
> No. '/dev/...' is a Linux thing and doesn't belong in DT.
> 
> You should define a partition UUID and/or label and the kernel can find 
> the right partition to use.
> 

pstore/blk do general read/write by filp_open/kernel_read/kernel_write,
which need device path.
In addition, i have no idea how to use UUID and/or label to do general
read/write on kernel layer, can you give me a tip?

>> +
>> +- dmesg-size: maximum size in kbytes of each dump done on oops, which must be a
>> +  multiple of 4.
>> +
>> +- pmsg-size: maximum size in kbytes for userspace messages, which must be a
>> +  multiple of 4.
> 
> Common properties shared with ramoops should be in a common doc.
> 

The size limit are different. Size for ramoops must be power of 2, but
be a multiple of 4k for pstore/blk.

> Rob
> 

-- 
liaoweixiong