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    Subject[PATCH 4/5] remoteproc: Introduce deny_sysfs_ops flag
    Date
    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'. 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 deny the sysfs state/firmware change by introducing
    a state flag 'deny_sysfs_ops' that the individual remoteproc drivers
    can set based on their usage needs. The default behavior is to
    allow the sysfs operations as before.

    Signed-off-by: Suman Anna <s-anna@ti.com>
    ---
    drivers/remoteproc/remoteproc_sysfs.c | 8 ++++++++
    include/linux/remoteproc.h | 2 ++
    2 files changed, 10 insertions(+)

    diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
    index ce93f4d710f3..b2d8c11b89d0 100644
    --- a/drivers/remoteproc/remoteproc_sysfs.c
    +++ b/drivers/remoteproc/remoteproc_sysfs.c
    @@ -36,6 +36,10 @@ static ssize_t firmware_store(struct device *dev,
    char *p;
    int err, len = count;

    + /* restrict sysfs operations if not allowed by remoteproc drivers */
    + if (rproc->deny_sysfs_ops)
    + return -EPERM;
    +
    err = mutex_lock_interruptible(&rproc->lock);
    if (err) {
    dev_err(dev, "can't lock rproc %s: %d\n", rproc->name, err);
    @@ -102,6 +106,10 @@ static ssize_t state_store(struct device *dev,
    struct rproc *rproc = to_rproc(dev);
    int ret = 0;

    + /* restrict sysfs operations if not allowed by remoteproc drivers */
    + if (rproc->deny_sysfs_ops)
    + return -EPERM;
    +
    if (sysfs_streq(buf, "start")) {
    if (rproc->state == RPROC_RUNNING)
    return -EBUSY;
    diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
    index 75f9ca05b865..d21252b4f758 100644
    --- a/include/linux/remoteproc.h
    +++ b/include/linux/remoteproc.h
    @@ -440,6 +440,7 @@ 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
    + * @deny_sysfs_ops: flag to not permit sysfs operations on state and firmware
    * @dump_segments: list of segments in the firmware
    */
    struct rproc {
    @@ -472,6 +473,7 @@ struct rproc {
    size_t table_sz;
    bool has_iommu;
    bool auto_boot;
    + bool deny_sysfs_ops;
    struct list_head dump_segments;
    };

    --
    2.18.0
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