From 07d66921337176e9d27e4d0a8a23425c8284a381 Mon Sep 17 00:00:00 2001 From: Khalid Aziz Date: Fri, 18 Jul 2014 09:15:40 -0600 Subject: [PATCH] sparc: Add support for seek and shorter read to /dev/mdesc /dev/mdesc on Linux does not support reading arbitrary number of bytes and seeking while /dev/mdesc on Solaris does. This causes tools that work on Solaris to break on Linux. This patch adds these two capabilities to /dev/mdesc. Signed-off-by: Khalid Aziz Acked-by: Sam Ravnborg Signed-off-by: David S. Miller --- arch/sparc/kernel/mdesc.c | 82 ++++++++++++++++++++++++++++++++------- 1 file changed, 69 insertions(+), 13 deletions(-) diff --git a/arch/sparc/kernel/mdesc.c b/arch/sparc/kernel/mdesc.c index a1a4400d4025..99632a87e697 100644 --- a/arch/sparc/kernel/mdesc.c +++ b/arch/sparc/kernel/mdesc.c @@ -906,29 +906,85 @@ void mdesc_fill_in_cpu_data(cpumask_t *mask) smp_fill_in_sib_core_maps(); } -static ssize_t mdesc_read(struct file *file, char __user *buf, - size_t len, loff_t *offp) +/* mdesc_open() - Grab a reference to mdesc_handle when /dev/mdesc is + * opened. Hold this reference until /dev/mdesc is closed to ensure + * mdesc data structure is not released underneath us. Store the + * pointer to mdesc structure in private_data for read and seek to use + */ +static int mdesc_open(struct inode *inode, struct file *file) { struct mdesc_handle *hp = mdesc_grab(); - int err; if (!hp) return -ENODEV; - err = hp->handle_size; - if (len < hp->handle_size) - err = -EMSGSIZE; - else if (copy_to_user(buf, &hp->mdesc, hp->handle_size)) - err = -EFAULT; - mdesc_release(hp); + file->private_data = hp; + + return 0; +} + +static ssize_t mdesc_read(struct file *file, char __user *buf, + size_t len, loff_t *offp) +{ + struct mdesc_handle *hp = file->private_data; + unsigned char *mdesc; + int bytes_left, count = len; + + if (*offp >= hp->handle_size) + return 0; + + bytes_left = hp->handle_size - *offp; + if (count > bytes_left) + count = bytes_left; + + mdesc = (unsigned char *)&hp->mdesc; + mdesc += *offp; + if (!copy_to_user(buf, mdesc, count)) { + *offp += count; + return count; + } else { + return -EFAULT; + } +} - return err; +static loff_t mdesc_llseek(struct file *file, loff_t offset, int whence) +{ + struct mdesc_handle *hp; + + switch (whence) { + case SEEK_CUR: + offset += file->f_pos; + break; + case SEEK_SET: + break; + default: + return -EINVAL; + } + + hp = file->private_data; + if (offset > hp->handle_size) + return -EINVAL; + else + file->f_pos = offset; + + return offset; +} + +/* mdesc_close() - /dev/mdesc is being closed, release the reference to + * mdesc structure. + */ +static int mdesc_close(struct inode *inode, struct file *file) +{ + mdesc_release(file->private_data); + return 0; } static const struct file_operations mdesc_fops = { - .read = mdesc_read, - .owner = THIS_MODULE, - .llseek = noop_llseek, + .open = mdesc_open, + .read = mdesc_read, + .llseek = mdesc_llseek, + .release = mdesc_close, + .owner = THIS_MODULE, }; static struct miscdevice mdesc_misc = { -- 2.34.1