/dev/port only supports reading and writing 8-bit ports; multi-byte operations on /dev/port will just operate on multiple successive 8-bit ports.
Add a new device, /dev/ioports, which supports reading and writing 16-bit and 32-bit ports. This makes it possible to perform arbitrary I/O port operations cleanly from privileged userspace processes, without using iopl or ioperm. Signed-off-by: Josh Triplett <[email protected]> --- Written after encountering yet another out-of-tree omnibus "do arbitrary I/O for test purposes" driver; this one's main reason for existence was the inability to operate on 16-bit and 32-bit I/O ports. Let's get a proper interface into the kernel, to make such drivers obsolete. I've also written a corresponding manpage patch, which I'll submit as a reply to this one. drivers/char/mem.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 77 insertions(+), 2 deletions(-) diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 917403f..84e0526 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -35,6 +35,7 @@ #endif #define DEVPORT_MINOR 4 +#define DEVIOPORTS_MINOR 12 static inline unsigned long size_inside_page(unsigned long start, unsigned long size) @@ -584,6 +585,69 @@ static ssize_t write_port(struct file *file, const char __user *buf, *ppos = i; return tmp-buf; } + +static ssize_t read_ioports(struct file *file, char __user *buf, + size_t count, loff_t *ppos) +{ + unsigned long port = *ppos; + + if (!access_ok(VERIFY_WRITE, buf, count)) + return -EFAULT; + if (port > 65535) + return 0; + switch (count) { + case 1: + if (__put_user(inb(port), buf) < 0) + return -EFAULT; + return 1; + case 2: + if (__put_user(inw(port), buf) < 0) + return -EFAULT; + return 2; + case 4: + if (__put_user(inl(port), buf) < 0) + return -EFAULT; + return 4; + default: + return -EINVAL; + } +} + +static ssize_t write_ioports(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + unsigned long port = *ppos; + + if (!access_ok(VERIFY_READ, buf, count)) + return -EFAULT; + if (port > 65535) + return 0; + switch (count) { + case 1: { + u8 b; + if (__get_user(b, buf)) + return -EFAULT; + outb(b, port); + return 1; + } + case 2: { + u16 w; + if (__get_user(w, buf)) + return -EFAULT; + outw(w, port); + return 2; + } + case 4: { + u32 l; + if (__get_user(l, buf)) + return -EFAULT; + outl(l, port); + return 4; + } + default: + return -EINVAL; + } +} #endif static ssize_t read_null(struct file *file, char __user *buf, @@ -779,6 +843,13 @@ static const struct file_operations port_fops = { .write = write_port, .open = open_port, }; + +static const struct file_operations ioports_fops = { + .llseek = memory_lseek, + .read = read_ioports, + .write = write_ioports, + .open = open_port, +}; #endif static const struct file_operations zero_fops = { @@ -827,6 +898,9 @@ static const struct memdev { #ifdef CONFIG_PRINTK [11] = { "kmsg", 0644, &kmsg_fops, NULL }, #endif +#ifdef CONFIG_DEVPORT + [12] = { "ioports", 0, &ioports_fops, NULL }, +#endif }; static int memory_open(struct inode *inode, struct file *filp) @@ -892,9 +966,10 @@ static int __init chr_dev_init(void) continue; /* - * Create /dev/port? + * Create /dev/port and /dev/ioports? */ - if ((minor == DEVPORT_MINOR) && !arch_has_dev_port()) + if ((minor == DEVPORT_MINOR || minor == DEVIOPORTS_MINOR) + && !arch_has_dev_port()) continue; device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor), -- 2.0.0.rc2 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
