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Date: Thu, 28 Jul 2016 16:10:59 -0500
From: Rob Herring <robh@...nel.org>
To: Kees Cook <keescook@...omium.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
Greg Hackmann <ghackmann@...gle.com>,
Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] Revert "pstore/ram: add Device Tree bindings"
On Thu, Jul 28, 2016 at 3:50 PM, Kees Cook <keescook@...omium.org> wrote:
> On Thu, Jul 28, 2016 at 1:25 PM, Rob Herring <robh@...nel.org> wrote:
>> This reverts commit 35da60941e44dbf57868e67686dd24cc1a33125a.
>> ---
>> WTF!
>>
>> I don't recall acking this nor have my comments (Arnd's really) been
>> addressed[1]. This should not have been merged yet.
>
> The conversation seemed to me to describe an alternative that could be
> moved to, but that it was going to need more work. In the meantime,
> these are the DT bindings used in real devices already. It seemed
> clear to me that reducing the delta now and improving the
> implementation in the future was the right thing to do in this case. I
> didn't think your comments were a hard NAK, but rather a "we should do
> this in the future", and I added it as a TODO for the pstore tree.
>
> Is a revert really justified here? This doesn't break anything (quite
> the opposite, actually).
Yes. Bindings are an ABI, so they can't evolve other than get
additional properties.
I'm keen to have this in too because I know there are lots of users
(extract a DT from a Calxeda system ;)). It's not really that far off
(drop memory-region and define the location in /reserved-memory) I
think. So send a follow-up for 4.8 and then it doesn't need a revert.
Rob
>
> -Kees
>
>>
>> Rob
>>
>> [1] https://lkml.org/lkml/2016/6/21/969
>>
>> Documentation/devicetree/bindings/misc/ramoops.txt | 48 -----------
>> Documentation/ramoops.txt | 6 +-
>> fs/pstore/ram.c | 95 +---------------------
>> 3 files changed, 4 insertions(+), 145 deletions(-)
>> delete mode 100644 Documentation/devicetree/bindings/misc/ramoops.txt
>>
>> diff --git a/Documentation/devicetree/bindings/misc/ramoops.txt b/Documentation/devicetree/bindings/misc/ramoops.txt
>> deleted file mode 100644
>> index cd02cec..0000000
>> --- a/Documentation/devicetree/bindings/misc/ramoops.txt
>> +++ /dev/null
>> @@ -1,48 +0,0 @@
>> -Ramoops oops/panic logger
>> -=========================
>> -
>> -ramoops provides persistent RAM storage for oops and panics, so they can be
>> -recovered after a reboot. It is a backend to pstore, so this node is named
>> -"ramoops" after the backend, rather than "pstore" which is the subsystem.
>> -
>> -Parts of this storage may be set aside for other persistent log buffers, such
>> -as kernel log messages, or for optional ECC error-correction data. The total
>> -size of these optional buffers must fit in the reserved region.
>> -
>> -Any remaining space will be used for a circular buffer of oops and panic
>> -records. These records have a configurable size, with a size of 0 indicating
>> -that they should be disabled.
>> -
>> -At least one of "record-size", "console-size", "ftrace-size", or "pmsg-size"
>> -must be set non-zero, but are otherwise optional as listed below.
>> -
>> -
>> -Required properties:
>> -
>> -- compatible: must be "ramoops"
>> -
>> -- memory-region: phandle to a region of memory that is preserved between
>> - reboots
>> -
>> -
>> -Optional properties:
>> -
>> -- ecc-size: enables ECC support and specifies ECC buffer size in bytes
>> - (defaults to 0: no ECC)
>> -
>> -- record-size: maximum size in bytes of each dump done on oops/panic
>> - (defaults to 0: disabled)
>> -
>> -- console-size: size in bytes of log buffer reserved for kernel messages
>> - (defaults to 0: disabled)
>> -
>> -- ftrace-size: size in bytes of log buffer reserved for function tracing and
>> - profiling (defaults to 0: disabled)
>> -
>> -- pmsg-size: size in bytes of log buffer reserved for userspace messages
>> - (defaults to 0: disabled)
>> -
>> -- unbuffered: if present, use unbuffered mappings to map the reserved region
>> - (defaults to buffered mappings)
>> -
>> -- no-dump-oops: if present, only dump panics (defaults to panics and oops)
>> diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt
>> index 9264bca..5d86756 100644
>> --- a/Documentation/ramoops.txt
>> +++ b/Documentation/ramoops.txt
>> @@ -45,7 +45,7 @@ corrupt, but usually it is restorable.
>>
>> 2. Setting the parameters
>>
>> -Setting the ramoops parameters can be done in 3 different manners:
>> +Setting the ramoops parameters can be done in 2 different manners:
>> 1. Use the module parameters (which have the names of the variables described
>> as before).
>> For quick debugging, you can also reserve parts of memory during boot
>> @@ -54,9 +54,7 @@ Setting the ramoops parameters can be done in 3 different manners:
>> kernel to use only the first 128 MB of memory, and place ECC-protected ramoops
>> region at 128 MB boundary:
>> "mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1"
>> - 2. Use Device Tree bindings, as described in
>> - Documentation/device-tree/bindings/misc/ramoops.txt.
>> - 3. Use a platform device and set the platform data. The parameters can then
>> + 2. Use a platform device and set the platform data. The parameters can then
>> be set through that platform data. An example of doing that is:
>>
>> #include <linux/pstore_ram.h>
>> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
>> index 47516a7..d9668c2 100644
>> --- a/fs/pstore/ram.c
>> +++ b/fs/pstore/ram.c
>> @@ -34,8 +34,6 @@
>> #include <linux/slab.h>
>> #include <linux/compiler.h>
>> #include <linux/pstore_ram.h>
>> -#include <linux/of.h>
>> -#include <linux/of_address.h>
>>
>> #define RAMOOPS_KERNMSG_HDR "===="
>> #define MIN_MEM_SIZE 4096UL
>> @@ -460,98 +458,15 @@ static int ramoops_init_prz(struct device *dev, struct ramoops_context *cxt,
>> return 0;
>> }
>>
>> -static int ramoops_parse_dt_size(struct platform_device *pdev,
>> - const char *propname, u32 *value)
>> -{
>> - u32 val32 = 0;
>> - int ret;
>> -
>> - ret = of_property_read_u32(pdev->dev.of_node, propname, &val32);
>> - if (ret < 0 && ret != -EINVAL) {
>> - dev_err(&pdev->dev, "failed to parse property %s: %d\n",
>> - propname, ret);
>> - return ret;
>> - }
>> -
>> - if (val32 > INT_MAX) {
>> - dev_err(&pdev->dev, "%s %u > INT_MAX\n", propname, val32);
>> - return -EOVERFLOW;
>> - }
>> -
>> - *value = val32;
>> - return 0;
>> -}
>> -
>> -static int ramoops_parse_dt(struct platform_device *pdev,
>> - struct ramoops_platform_data *pdata)
>> -{
>> - struct device_node *of_node = pdev->dev.of_node;
>> - struct device_node *mem_region;
>> - struct resource res;
>> - u32 value;
>> - int ret;
>> -
>> - dev_dbg(&pdev->dev, "using Device Tree\n");
>> -
>> - mem_region = of_parse_phandle(of_node, "memory-region", 0);
>> - if (!mem_region) {
>> - dev_err(&pdev->dev, "no memory-region phandle\n");
>> - return -ENODEV;
>> - }
>> -
>> - ret = of_address_to_resource(mem_region, 0, &res);
>> - of_node_put(mem_region);
>> - if (ret) {
>> - dev_err(&pdev->dev,
>> - "failed to translate memory-region to resource: %d\n",
>> - ret);
>> - return ret;
>> - }
>> -
>> - pdata->mem_size = resource_size(&res);
>> - pdata->mem_address = res.start;
>> - pdata->mem_type = of_property_read_bool(of_node, "unbuffered");
>> - pdata->dump_oops = !of_property_read_bool(of_node, "no-dump-oops");
>> -
>> -#define parse_size(name, field) { \
>> - ret = ramoops_parse_dt_size(pdev, name, &value); \
>> - if (ret < 0) \
>> - return ret; \
>> - field = value; \
>> - }
>> -
>> - parse_size("record-size", pdata->record_size);
>> - parse_size("console-size", pdata->console_size);
>> - parse_size("ftrace-size", pdata->ftrace_size);
>> - parse_size("pmsg-size", pdata->pmsg_size);
>> - parse_size("ecc-size", pdata->ecc_info.ecc_size);
>> -
>> -#undef parse_size
>> -
>> - return 0;
>> -}
>> -
>> static int ramoops_probe(struct platform_device *pdev)
>> {
>> struct device *dev = &pdev->dev;
>> - struct ramoops_platform_data *pdata = dev->platform_data;
>> + struct ramoops_platform_data *pdata = pdev->dev.platform_data;
>> struct ramoops_context *cxt = &oops_cxt;
>> size_t dump_mem_sz;
>> phys_addr_t paddr;
>> int err = -EINVAL;
>>
>> - if (dev_of_node(dev) && !pdata) {
>> - pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
>> - if (!pdata) {
>> - err = -ENOMEM;
>> - goto fail_out;
>> - }
>> -
>> - err = ramoops_parse_dt(pdev, pdata);
>> - if (err < 0)
>> - goto fail_out;
>> - }
>> -
>> /* Only a single ramoops area allowed at a time, so fail extra
>> * probes.
>> */
>> @@ -681,17 +596,11 @@ static int ramoops_remove(struct platform_device *pdev)
>> return 0;
>> }
>>
>> -static const struct of_device_id dt_match[] = {
>> - { .compatible = "ramoops" },
>> - {}
>> -};
>> -
>> static struct platform_driver ramoops_driver = {
>> .probe = ramoops_probe,
>> .remove = ramoops_remove,
>> .driver = {
>> - .name = "ramoops",
>> - .of_match_table = dt_match,
>> + .name = "ramoops",
>> },
>> };
>>
>> --
>> 2.9.2
>>
>
>
>
> --
> Kees Cook
> Chrome OS & Brillo Security
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