linux-kernel - Re: [PATCH v2 3/4] remoteproc: Add a sysfs interface for firmware and state

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Date:   Wed, 19 Oct 2016 12:04:58 +0100
From:   Matt Redfearn <matt.redfearn@...tec.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
CC:     Ohad Ben-Cohen <ohad@...ery.com>,
        <linux-remoteproc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] remoteproc: Add a sysfs interface for firmware and
 state

Hi Bjorn,


On 18/10/16 23:16, Bjorn Andersson wrote:
> On Mon 17 Oct 08:49 PDT 2016, Matt Redfearn wrote:
>
>> This patch adds a sysfs interface to rproc allowing the firmware name
>> and processor state to be changed dynamically.
>>
>> State was previously available in debugfs, and is replicated here. The
>> firmware file allows retrieval of the running firmware name, and a new
>> one to be specified at run time, so long as the remote processor has
>> been stopped.
>>
>> Signed-off-by: Matt Redfearn <matt.redfearn@...tec.com>
>>
>> ---
>>
>> Changes in v2:
>> Have firmware_store perform the necessary steps inline.
>> Use sysfs_streq when dealing with writes to sysfs files
>>
> [..]
>> diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
>> new file mode 100644
>> index 000000000000..afa9ca040a7e
>> --- /dev/null
>> +++ b/drivers/remoteproc/remoteproc_sysfs.c
>> @@ -0,0 +1,155 @@
>> +/*
>> + * Remote Processor Framework
>> + *
>> + * This program is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU General Public License
>> + * version 2 as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + */
>> +
>> +#include <linux/remoteproc.h>
>> +
>> +#include "remoteproc_internal.h"
>> +
>> +#define to_rproc(d) container_of(d, struct rproc, dev)
>> +
>> +/* Expose the loaded / running firmware name via sysfs */
>> +static ssize_t firmware_show(struct device *dev, struct device_attribute *attr,
>> +			  char *buf)
>> +{
>> +	struct rproc *rproc = to_rproc(dev);
>> +
>> +	return sprintf(buf, "%s\n", rproc->firmware);
>> +}
>> +
>> +/* Change firmware name via sysfs */
>> +static ssize_t firmware_store(struct device *dev,
>> +			      struct device_attribute *attr,
>> +			      const char *buf, size_t count)
>> +{
>> +	struct rproc *rproc = to_rproc(dev);
>> +	char *p;
>> +	int err, len = count;
>> +
>> +	err = mutex_lock_interruptible(&rproc->lock);
>> +	if (err) {
>> +		dev_err(dev, "can't lock rproc %s: %d\n", rproc->name, err);
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (rproc->state != RPROC_OFFLINE) {
>> +		dev_err(dev, "can't change firmware while running\n");
>> +		err = -EBUSY;
>> +		goto out;
>> +	}
>> +
>> +	p = memchr(buf, '\n', count);
>> +	if (p)
>> +		len = p - buf;
> I prefer the following variant:
>
> len = strcspn(buf, '\n');

Yes - that's neater.

>
>> +
>> +	p = kstrndup(buf, len, GFP_KERNEL);
>> +	if (!p) {
>> +		err = -ENOMEM;
>> +		goto out;
>> +	}
>> +
>> +	kfree(rproc->firmware);
>> +	rproc->firmware = p;
>> +
>> +	err = rproc_add_virtio_devices(rproc);
> As of v4.9 rproc_add_virtio_devices() will only check to see if the
> rproc driver has auto_boot set and if so boot the core. (Yes it needs a
> new name)
>
> Also I'm not sure if it's valid to provide a sysfs API like this and
> sometimes setting firmware results in rproc_boot() and sometimes not...
>
> So, just drop patch 2 in this series and drop the call to
> rproc_add_virtio_devices() here.

Makes sense, and it's more consistent behavior with that change.

>
>> +out:
>> +	mutex_unlock(&rproc->lock);
>> +
>> +	return err ? err : count;
>> +}
>> +static DEVICE_ATTR_RW(firmware);
>> +
>> +/*
>> + * A state-to-string lookup table, for exposing a human readable state
>> + * via sysfs. Always keep in sync with enum rproc_state
>> + */
>> +static const char * const rproc_state_string[] = {
>> +	"offline",
> Please be overly explicit here and make these:
>
> 	[RPROC_OFFLINE] = "offline",

No problem.

Thanks,
Matt

>
>> +	"suspended",
>> +	"running",
>> +	"crashed",
>> +	"invalid",
>> +};
>> +
> Regards,
> Bjorn