On Wed, Feb 13, 2019 at 7:51 AM liaoweixiong
[off-list ref] wrote:

On 2019-01-31 00:07, Rob Herring wrote:> On Wed, Jan 23, 2019 at
08:05:13PM +0800, liaoweixiong wrote:

quoted

quoted

Create DT binding document for blkoops.

Signed-off-by: liaoweixiong <redacted>
---
 .../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.

quoted

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 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.

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+
+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.

The partition table says how big a partition is. If you only want to
use part of it, then make the partition smaller or use a file system.
This is a solved problem, so we don't need a new way in DT to handle
this.

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+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?

The kernel can mount a filesystem by label or UUID though I think
those are filesystem UUID and label, not partition UUID and label. But
certainly bootloaders find the EFI system partition by UUID.

Rob