[PATCH 1/4] hwrng: core - drop unnecessary forward declarations

[PATCH 1/4] hwrng: core - drop unnecessary forward declarations

[Thorsten Blum]

The forward declarations for drop_current_rng() and rng_get_data() are
not needed - remove them.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 drivers/char/hw_random/core.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index aba92d777f72..68add1a97f31 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -54,13 +54,9 @@ module_param(default_quality, ushort, 0644);
 MODULE_PARM_DESC(default_quality,
 		 "default maximum entropy content of hwrng per 1024 bits of input");
 
-static void drop_current_rng(void);
 static int hwrng_init(struct hwrng *rng);
 static int hwrng_fillfn(void *unused);
 
-static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
-			       int wait);
-
 static size_t rng_buffer_size(void)
 {
 	return RNG_BUFFER_SIZE;

[PATCH 2/4] hwrng: core - use bool for wait parameter in rng_get_data

[Thorsten Blum]

The 'wait' parameter in rng_get_data() is a boolean flag - use bool
instead of int to better reflect its actual type.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 drivers/char/hw_random/core.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 68add1a97f31..905a63525831 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -211,7 +211,7 @@ static int rng_dev_open(struct inode *inode, struct file *filp)
 }
 
 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
-			int wait) {
+			bool wait) {
 	int present;
 
 	BUG_ON(!mutex_is_locked(&reading_mutex));
@@ -534,8 +534,7 @@ static int hwrng_fillfn(void *unused)
 		}
 
 		mutex_lock(&reading_mutex);
-		rc = rng_get_data(rng, rng_fillbuf,
-				  rng_buffer_size(), 1);
+		rc = rng_get_data(rng, rng_fillbuf, rng_buffer_size(), true);
 		if (current_quality != rng->quality)
 			rng->quality = current_quality; /* obsolete */
 		quality = rng->quality;

Re: [PATCH 2/4] hwrng: core - use bool for wait parameter in rng_get_data

[Andy Shevchenko]

On Thu, Apr 30, 2026 at 01:00:49PM +0200, Thorsten Blum wrote:
> The 'wait' parameter in rng_get_data() is a boolean flag - use bool
> instead of int to better reflect its actual type.

...

>  static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
> -			int wait) {
> +			bool wait) {

You want to fix the checkpatch warnings while at it and indentation.

static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
			       bool wait)
{

...

> -		rc = rng_get_data(rng, rng_fillbuf,
> -				  rng_buffer_size(), 1);
> +		rc = rng_get_data(rng, rng_fillbuf, rng_buffer_size(), true);

Is it the only user? Why parameter is needed at all?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 2/4] hwrng: core - use bool for wait parameter in rng_get_data

[Thorsten Blum]

On Mon, May 04, 2026 at 03:54:14PM +0200, Andy Shevchenko wrote:
> On Thu, Apr 30, 2026 at 01:00:49PM +0200, Thorsten Blum wrote:
> > The 'wait' parameter in rng_get_data() is a boolean flag - use bool
> > instead of int to better reflect its actual type.
> 
> ...
> 
> >  static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
> > -			int wait) {
> > +			bool wait) {
> 
> You want to fix the checkpatch warnings while at it and indentation.

I just checked again, but I don't get any checkpatch warnings.

> static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
> 			       bool wait)
> {
> 
> ...
> 
> > -		rc = rng_get_data(rng, rng_fillbuf,
> > -				  rng_buffer_size(), 1);
> > +		rc = rng_get_data(rng, rng_fillbuf, rng_buffer_size(), true);
> 
> Is it the only user? Why parameter is needed at all?

The other one in rng_dev_read() already uses a boolean expression, hence
no changes.

Thanks,
Thorsten

Re: [PATCH 2/4] hwrng: core - use bool for wait parameter in rng_get_data

[Andy Shevchenko]

On Mon, May 04, 2026 at 04:37:17PM +0200, Thorsten Blum wrote:
> On Mon, May 04, 2026 at 03:54:14PM +0200, Andy Shevchenko wrote:
> > On Thu, Apr 30, 2026 at 01:00:49PM +0200, Thorsten Blum wrote:

...

> > >  static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
> > > -			int wait) {
> > > +			bool wait) {
> > 
> > You want to fix the checkpatch warnings while at it and indentation.
> 
> I just checked again, but I don't get any checkpatch warnings.

Hmm... I remember for sure that checkpatch warns when it's a { on the line of
the prototype... Maybe it's about different scenario. Whatever, the coding
style is to have { on the new line.

...

> > > -		rc = rng_get_data(rng, rng_fillbuf,
> > > -				  rng_buffer_size(), 1);
> > > +		rc = rng_get_data(rng, rng_fillbuf, rng_buffer_size(), true);
> > 
> > Is it the only user? Why parameter is needed at all?
> 
> The other one in rng_dev_read() already uses a boolean expression, hence
> no changes.

Good, thanks for clarification.

-- 
With Best Regards,
Andy Shevchenko

[PATCH 3/4] hwrng: core - use MAX to simplify RNG_BUFFER_SIZE

[Thorsten Blum]

Replace the open-coded variant with MAX().

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 drivers/char/hw_random/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 905a63525831..f8f7a2ee73c1 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -17,6 +17,7 @@
 #include <linux/hw_random.h>
 #include <linux/kernel.h>
 #include <linux/kthread.h>
+#include <linux/minmax.h>
 #include <linux/miscdevice.h>
 #include <linux/module.h>
 #include <linux/random.h>
@@ -30,7 +31,7 @@
 
 #define RNG_MODULE_NAME		"hw_random"
 
-#define RNG_BUFFER_SIZE (SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES)
+#define RNG_BUFFER_SIZE		MAX(32, SMP_CACHE_BYTES)
 
 static struct hwrng __rcu *current_rng;
 /* the current rng has been explicitly chosen by user via sysfs */

Re: [PATCH 3/4] hwrng: core - use MAX to simplify RNG_BUFFER_SIZE

[Andy Shevchenko]

On Thu, Apr 30, 2026 at 01:00:50PM +0200, Thorsten Blum wrote:
> Replace the open-coded variant with MAX().

Hmm... While this patch is correct the very similar is being used
outside of hwrng. Can we perhaps have a common definition somewhere
near to SMP_CACHE_BYTES?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 3/4] hwrng: core - use MAX to simplify RNG_BUFFER_SIZE

[Herbert Xu]

On Thu, Apr 30, 2026 at 01:00:50PM +0200, Thorsten Blum wrote:
> Replace the open-coded variant with MAX().
> 
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
>  drivers/char/hw_random/core.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> index 905a63525831..f8f7a2ee73c1 100644
> --- a/drivers/char/hw_random/core.c
> +++ b/drivers/char/hw_random/core.c
> @@ -17,6 +17,7 @@
>  #include <linux/hw_random.h>
>  #include <linux/kernel.h>
>  #include <linux/kthread.h>
> +#include <linux/minmax.h>

No need for minmax.h because kernel.h already includes it.

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

[PATCH 4/4] hwrng: core - use sysfs_emit_at in rng_available_show

[Thorsten Blum]

Replace strlcat() with sysfs_emit_at() in rng_available_show() and add
'int len' to keep track of the number of bytes written. sysfs_emit_at()
is preferred for formatting sysfs output because it provides safer
bounds checking.

Inline mutex_lock_interruptible() and drop the now-unused local error
variable. Remove the unnecessary 'buf' NUL initialization. Return 'len'
directly instead of strlen(buf).

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 drivers/char/hw_random/core.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index f8f7a2ee73c1..1d1ea4ebde31 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -26,6 +26,7 @@
 #include <linux/sched/signal.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/sysfs.h>
 #include <linux/uaccess.h>
 #include <linux/workqueue.h>
 
@@ -415,21 +416,17 @@ static ssize_t rng_available_show(struct device *dev,
 				  struct device_attribute *attr,
 				  char *buf)
 {
-	int err;
 	struct hwrng *rng;
+	int len = 0;
 
-	err = mutex_lock_interruptible(&rng_mutex);
-	if (err)
+	if (mutex_lock_interruptible(&rng_mutex))
 		return -ERESTARTSYS;
-	buf[0] = '\0';
-	list_for_each_entry(rng, &rng_list, list) {
-		strlcat(buf, rng->name, PAGE_SIZE);
-		strlcat(buf, " ", PAGE_SIZE);
-	}
-	strlcat(buf, "none\n", PAGE_SIZE);
+	list_for_each_entry(rng, &rng_list, list)
+		len += sysfs_emit_at(buf, len, "%s ", rng->name);
+	len += sysfs_emit_at(buf, len, "none\n");
 	mutex_unlock(&rng_mutex);
 
-	return strlen(buf);
+	return len;
 }
 
 static ssize_t rng_selected_show(struct device *dev,

Re: [PATCH 4/4] hwrng: core - use sysfs_emit_at in rng_available_show

[Andy Shevchenko]

On Thu, Apr 30, 2026 at 01:00:51PM +0200, Thorsten Blum wrote:
> Replace strlcat() with sysfs_emit_at() in rng_available_show() and add
> 'int len' to keep track of the number of bytes written. sysfs_emit_at()
> is preferred for formatting sysfs output because it provides safer
> bounds checking.
> 
> Inline mutex_lock_interruptible() and drop the now-unused local error
> variable. Remove the unnecessary 'buf' NUL initialization. Return 'len'
> directly instead of strlen(buf).

This is almost the same I came up with (but only today), hence
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>

Also note, when series is more than a single patch, it's highly recommended to
have a cover letter. Some maintainers do even require that.

-- 
With Best Regards,
Andy Shevchenko