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Message-ID: <869aa1ad-e3ed-cd0b-ab5e-a4b7d1d23311@ti.com>
Date:   Thu, 3 Mar 2022 13:30:08 +0530
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Subject: Re: [EXTERNAL] Re: [PATCH v5 1/2] remoteproc: Introduce
 sysfs_read_only flag
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To:     Bjorn Andersson <bjorn.andersson@linaro.org>,
        Kishon Vijay Abraham I <kishon@ti.com>
CC:     <vigneshr@ti.com>, <s-anna@ti.com>, <mathieu.poirier@linaro.org>,
        <linux-remoteproc@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>
References: <20220216081224.9956-1-p-mohan@ti.com>
 <20220216081224.9956-2-p-mohan@ti.com>
 <0d44d73f-d882-83db-9cf2-09f7cdc91ab2@ti.com> <Yg80gABeszDDN/m6@ripper>
From:   Puranjay Mohan <p-mohan@ti.com>
In-Reply-To: <Yg80gABeszDDN/m6@ripper>
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Hi Bjorn,
Hi Mathieu,

When is this series expected to be applied?

I am going to post another series titled "PRU Consumer API".
One patch from that series depends on this "Introduce sysfs_read_only
flag" patch.

Please let me know so I can rebase and post that series.

Thanks,
Puranjay Mohan

On 18/02/22 11:24, Bjorn Andersson wrote:
> On Thu 17 Feb 21:00 PST 2022, Kishon Vijay Abraham I wrote:
> 
>>
>>
>> On 16/02/22 1:42 pm, Puranjay Mohan wrote:
>>> The remoteproc framework provides sysfs interfaces for changing
>>> the firmware name and for starting/stopping a remote processor
>>> through the sysfs files 'state' and 'firmware'. The 'coredump'
>>> file is used to set the coredump configuration. The 'recovery'
>>> sysfs file can also be used similarly to control the error recovery
>>> state machine of a remoteproc. These interfaces are currently
>>> allowed irrespective of how the remoteprocs were booted (like
>>> remoteproc self auto-boot, remoteproc client-driven boot etc).
>>> These interfaces can adversely affect a remoteproc and its clients
>>> especially when a remoteproc is being controlled by a remoteproc
>>> client driver(s). Also, not all remoteproc drivers may want to
>>> support the sysfs interfaces by default.
>>>
>>> Add support to make the remoteproc sysfs files read only by
>>> introducing a state flag 'sysfs_read_only' that the individual
>>> remoteproc drivers can set based on their usage needs. The default
>>> behavior is to allow the sysfs operations as before.
>>>
>>> Implement attribute_group->is_visible() to make the sysfs
>>> entries read only when 'sysfs_read_only' flag is set.
>>>
>>> Signed-off-by: Puranjay Mohan <p-mohan@ti.com>
>>> Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
>>> ---
>>> Changes in v4->v5:
>>> Rename deny_sysfs_ops to sysfs_read_only.
>>> Make coredump readonly with other files.
>>>
>>> Changes in v3->v4:
>>> Use mode = 0444 in rproc_is_visible() to make the sysfs entries
>>> read-only when the deny_sysfs_ops flag is set.
>>> ---
>>>  drivers/remoteproc/remoteproc_sysfs.c | 19 ++++++++++++++++++-
>>>  include/linux/remoteproc.h            |  2 ++
>>>  2 files changed, 20 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
>>> index ea8b89f97d7b..abf0cd05d5e1 100644
>>> --- a/drivers/remoteproc/remoteproc_sysfs.c
>>> +++ b/drivers/remoteproc/remoteproc_sysfs.c
>>> @@ -230,6 +230,22 @@ static ssize_t name_show(struct device *dev, struct device_attribute *attr,
>>>  }
>>>  static DEVICE_ATTR_RO(name);
>>>  
>>> +static umode_t rproc_is_visible(struct kobject *kobj, struct attribute *attr,
>>> +				int n)
>>> +{
>>> +	struct device *dev = kobj_to_dev(kobj);
>>> +	struct rproc *rproc = to_rproc(dev);
>>> +	umode_t mode = attr->mode;
>>> +
>>> +	if (rproc->sysfs_read_only && (attr == &dev_attr_recovery.attr ||
>>> +				       attr == &dev_attr_firmware.attr ||
>>> +				       attr == &dev_attr_state.attr ||
>>> +				       attr == &dev_attr_coredump.attr))
>>> +		mode = 0444;
>>
>> Nitpick: use S_IRUGO instead of 0444.
>>
> 
> Thanks for the suggestion Kishon, but I like 0444, it has direct meaning
> to me.
> 
> So unless there's some directive to use S_I*** throughout the kernel I
> would prefer this.
> 
> Regards,
> Bjorn
> 
>> Thanks,
>> Kishon
>>> +
>>> +	return mode;
>>> +}
>>> +
>>>  static struct attribute *rproc_attrs[] = {
>>>  	&dev_attr_coredump.attr,
>>>  	&dev_attr_recovery.attr,
>>> @@ -240,7 +256,8 @@ static struct attribute *rproc_attrs[] = {
>>>  };
>>>  
>>>  static const struct attribute_group rproc_devgroup = {
>>> -	.attrs = rproc_attrs
>>> +	.attrs = rproc_attrs,
>>> +	.is_visible = rproc_is_visible,
>>>  };
>>>  
>>>  static const struct attribute_group *rproc_devgroups[] = {
>>> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
>>> index e0600e1e5c17..93a1d0050fbc 100644
>>> --- a/include/linux/remoteproc.h
>>> +++ b/include/linux/remoteproc.h
>>> @@ -523,6 +523,7 @@ struct rproc_dump_segment {
>>>   * @table_sz: size of @cached_table
>>>   * @has_iommu: flag to indicate if remote processor is behind an MMU
>>>   * @auto_boot: flag to indicate if remote processor should be auto-started
>>> + * @sysfs_read_only: flag to make remoteproc sysfs files read only
>>>   * @dump_segments: list of segments in the firmware
>>>   * @nb_vdev: number of vdev currently handled by rproc
>>>   * @elf_class: firmware ELF class
>>> @@ -562,6 +563,7 @@ struct rproc {
>>>  	size_t table_sz;
>>>  	bool has_iommu;
>>>  	bool auto_boot;
>>> +	bool sysfs_read_only;
>>>  	struct list_head dump_segments;
>>>  	int nb_vdev;
>>>  	u8 elf_class;
>>>