# \[PATCH RFC 15/22\] xtensa: simdisk: let procfs copy in writes

- From: Christian Brauner \<brauner@kernel.org\>
- Date: 2026-11-02 15:06:37 
- List: linux-fbdev
- Page: https://ratatoskr.run/linux-fbdev/2026/11/17845369
- Thread: https://ratatoskr.run/linux-fsdevel/2026/11/17844895/t.md

```text
Implement ->proc_write_buf() so procfs copies in what is written to the
simdisk files before it pins the entry, and take the file name from
that copy. The files took up to PAGE_SIZE bytes and keep doing that
through ->proc_write_size.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 arch/xtensa/platforms/iss/simdisk.c | 26 ++++++++++----------------
 1 file changed, 10 insertions(+), 16 deletions(-)

diff --git a/arch/xtensa/platforms/iss/simdisk.c b/arch/xtensa/platforms/iss/simdisk.c
index 7b115e023de9..b2f9e7f3ade3 100644
--- a/arch/xtensa/platforms/iss/simdisk.c
+++ b/arch/xtensa/platforms/iss/simdisk.c
@@ -241,7 +241,7 @@ static ssize_t proc_read_simdisk(struct file *file, char __user *buf,
 	ssize_t len;
 	char *temp;
 
-	/* a write sets at most a page, see proc_write_simdisk() */
+	/* a write sets at most a page, see simdisk_proc_ops */
 	temp = kmalloc(PAGE_SIZE + 2, GFP_KERNEL);
 	if (!temp)
 		return -ENOMEM;
@@ -255,40 +255,34 @@ static ssize_t proc_read_simdisk(struct file *file, char __user *buf,
 	return len;
 }
 
-static ssize_t proc_write_simdisk(struct file *file, const char __user *buf,
+static ssize_t proc_write_simdisk(struct file *file, char *buf,
 			size_t count, loff_t *ppos)
 {
-	char *tmp;
 	struct simdisk *dev = pde_data(file_inode(file));
 	int err;
 
-	if (count == 0 || count > PAGE_SIZE)
+	if (count == 0)
 		return -EINVAL;
 
-	tmp = memdup_user_nul(buf, count);
-	if (IS_ERR(tmp))
-		return PTR_ERR(tmp);
-
 	err = simdisk_detach(dev);
 	if (err != 0)
-		goto out_free;
+		return err;
 
-	if (count > 0 && tmp[count - 1] == '\n')
-		tmp[count - 1] = 0;
+	if (count > 0 && buf[count - 1] == '\n')
+		buf[count - 1] = 0;
 
-	if (tmp[0])
-		err = simdisk_attach(dev, tmp);
+	if (buf[0])
+		err = simdisk_attach(dev, buf);
 
 	if (err == 0)
 		err = count;
-out_free:
-	kfree(tmp);
 	return err;
 }
 
 static const struct proc_ops simdisk_proc_ops = {
 	.proc_read	= proc_read_simdisk,
-	.proc_write	= proc_write_simdisk,
+	.proc_write_buf	= proc_write_simdisk,
+	.proc_write_size = PAGE_SIZE,
 	.proc_lseek	= default_llseek,
 };
 

-- 
2.53.0

```