On 3 July 2017 at 15:33, Harald Freudenberger <freude@xxxxxxxxxxxxxxxxxx> wrote: > This patch introduces a new sysfs attribute file 'rng_selected' > which shows the the rng chosen by userspace. > > If a rng source is chosen by user via echo some valid string > to rng_current there should be a way to signal this choice to > userspace. The new attribute file 'rng_selected' shows either > the name of the rng chosen or 'none'. > > Signed-off-by: Harald Freudenberger <freude@xxxxxxxxxxxxxxxxxx> > --- > drivers/char/hw_random/core.c | 22 +++++++++++++++++----- > 1 file changed, 17 insertions(+), 5 deletions(-) > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c > index ffd4e36..6a6276a 100644 > --- a/drivers/char/hw_random/core.c > +++ b/drivers/char/hw_random/core.c > @@ -28,8 +28,8 @@ > #define RNG_MODULE_NAME "hw_random" > > static struct hwrng *current_rng; > -/* the current rng has been explicitly chosen by user via sysfs */ > -static int cur_rng_set_by_user; > +/* the rng explicitly selected by user via sysfs */ > +static struct hwrng *selected_rng; > static struct task_struct *hwrng_fill; > /* list of registered rngs, sorted decending by quality */ > static LIST_HEAD(rng_list); > @@ -306,7 +306,7 @@ static ssize_t hwrng_attr_current_store(struct device *dev, > list_for_each_entry(rng, &rng_list, list) { > if (sysfs_streq(rng->name, buf)) { > err = 0; > - cur_rng_set_by_user = 1; > + selected_rng = rng; > if (rng != current_rng) > err = set_current_rng(rng); > break; > @@ -355,16 +355,28 @@ static ssize_t hwrng_attr_available_show(struct device *dev, > return strlen(buf); > } > > +static ssize_t hwrng_attr_selected_show(struct device *dev, > + struct device_attribute *attr, > + char *buf) > +{ > + return snprintf(buf, PAGE_SIZE, "%s\n", > + selected_rng ? selected_rng->name : "none"); > +} > + > static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR, > hwrng_attr_current_show, > hwrng_attr_current_store); > static DEVICE_ATTR(rng_available, S_IRUGO, > hwrng_attr_available_show, > NULL); > +static DEVICE_ATTR(rng_selected, S_IRUGO, > + hwrng_attr_selected_show, > + NULL); > > static struct attribute *rng_dev_attrs[] = { > &dev_attr_rng_current.attr, > &dev_attr_rng_available.attr, > + &dev_attr_rng_selected.attr, > NULL > }; > > @@ -448,7 +460,7 @@ int hwrng_register(struct hwrng *rng) > old_rng = current_rng; > err = 0; > if (!old_rng || > - (!cur_rng_set_by_user && rng->quality > old_rng->quality)) { > + (!selected_rng && rng->quality > old_rng->quality)) { > /* > * Set new rng as current as the new rng source > * provides better entropy quality and was not > @@ -484,7 +496,7 @@ void hwrng_unregister(struct hwrng *rng) > list_del(&rng->list); > if (current_rng == rng) { > drop_current_rng(); > - cur_rng_set_by_user = 0; > + selected_rng = NULL; > /* rng_list is sorted by quality, use the best (=first) one */ > if (!list_empty(&rng_list)) { > struct hwrng *new_rng; > -- > 2.7.4 > The current_rng sysfs attribute shows currently selected rng. So this new attribute can contain 1 to indicate user's choice, 0 otherwise. Regards, PrasannaKumar