tty: Add a new file /proc/tty/consoles (f4a3e0bc) · Commits · 戴 / test

Documentation/filesystems/proc.txt

+32 −0

Original line number	Diff line number	Diff line
		@@ -1075,6 +1075,7 @@ Table 1-11: Files in /proc/tty
		drivers list of drivers and their usage
		ldiscs registered line disciplines
		driver/serial usage statistic and status of single tty lines
		consoles registered system console lines
		..............................................................................

		To see which tty's are currently in use, you can simply look into the file
		@@ -1093,6 +1094,37 @@ To see which tty's are currently in use, you can simply look into the file
		/dev/tty /dev/tty 5 0 system:/dev/tty
		unknown /dev/tty 4 1-63 console

		To see which character device lines are currently used for the system console
		/dev/console, you may simply look into the file /proc/tty/consoles:

		> cat /proc/tty/consoles
		tty0 -WU (ECp) 4:7
		ttyS0 -W- (Ep) 4:64

		The columns are:

		device name of the device
		operations R = can do read operations
		W = can do write operations
		U = can do unblank
		flags E = it is enabled
		C = it is prefered console
		B = it is primary boot console
		p = it is used for printk buffer
		b = it is not a TTY but a Braille device
		a = it is safe to use when cpu is offline
		* = it is standard input of the reading process
		major:minor major and minor number of the device separated by a colon

		If the reading process holds /dev/console open at the regular standard input
		stream the active device will be marked by an asterisk:

		> cat /proc/tty/consoles < /dev/console
		tty0 -WU (ECp*) 4:7
		ttyS0 -W- (Ep) 4:64
		> tty
		/dev/pts/3


		1.8 Miscellaneous kernel statistics in /proc/stat
		-------------------------------------------------

fs/proc/proc_tty.c

+158 −0

Original line number	Diff line number	Diff line
		@@ -12,7 +12,10 @@
		#include <linux/proc_fs.h>
		#include <linux/stat.h>
		#include <linux/tty.h>
		#include <linux/tty_driver.h>
		#include <linux/console.h>
		#include <linux/seq_file.h>
		#include <linux/fdtable.h>
		#include <linux/bitops.h>

		/*
		@@ -136,6 +139,160 @@ static const struct file_operations proc_tty_drivers_operations = {
		.release = seq_release,
		};

		/*
		* The device ID of file descriptor 0 of the current reading
		* task if a character device...
		*/
		static dev_t current_dev;

		/*
		* This is the handler for /proc/tty/consoles
		*/
		static int show_console_dev(struct seq_file m, void v)
		{
		const struct tty_driver *driver;
		struct console *con;
		int index, len;
		char flags[10];
		dev_t dev;

		if (v == SEQ_START_TOKEN)
		return 0;
		con = (struct console *)v;
		if (!con)
		return 0;
		driver = con->device(con, &index);
		if (!driver)
		return 0;
		dev = MKDEV(driver->major, driver->minor_start) + index;

		index = 0;
		if (con->flags & CON_ENABLED)
		flags[index++] = 'E';
		if (con->flags & CON_CONSDEV)
		flags[index++] = 'C';
		if (con->flags & CON_BOOT)
		flags[index++] = 'B';
		if (con->flags & CON_PRINTBUFFER)
		flags[index++] = 'p';
		if (con->flags & CON_BRL)
		flags[index++] = 'b';
		if (con->flags & CON_ANYTIME)
		flags[index++] = 'a';
		if (current_dev == dev)
		flags[index++] = '*';
		flags[index] = 0;

		seq_printf(m, "%s%d%n", con->name, con->index, &len);
		len = 21 - len;
		if (len < 1)
		len = 1;
		seq_printf(m, "%*c", len, ' ');
		seq_printf(m, "%c%c%c (%s)%n", con->read ? 'R' : '-',
		con->write ? 'W' : '-', con->unblank ? 'U' : '-',
		flags, &len);
		len = 13 - len;
		if (len < 1)
		len = 1;
		seq_printf(m, "%*c%4d:%d\n", len, ' ', MAJOR(dev), MINOR(dev));

		return 0;
		}

		/* iterator for consoles */
		static void c_start(struct seq_file m, loff_t *pos)
		{
		struct console *con;
		loff_t off = 0;

		if (*pos == 0)
		return SEQ_START_TOKEN;

		acquire_console_sem();
		for (con = console_drivers; con; con = con->next) {
		if (!con->device)
		continue;
		if (++off == *pos)
		break;
		}
		release_console_sem();

		return con;
		}

		static void c_next(struct seq_file m, void v, loff_t pos)
		{
		struct console *con;

		acquire_console_sem();
		if (v == SEQ_START_TOKEN)
		con = console_drivers;
		else
		con = ((struct console *)v)->next;
		for (; con; con = con->next) {
		if (!con->device)
		continue;
		++*pos;
		break;
		}
		release_console_sem();

		return con;
		}

		static void c_stop(struct seq_file m, void v)
		{
		}

		static const struct seq_operations tty_consoles_op = {
		.start = c_start,
		.next = c_next,
		.stop = c_stop,
		.show = show_console_dev
		};

		/*
		* Used for open /proc/tty/consoles. Before this detect
		* the device ID of file descriptor 0 of the current
		* reading task if a character device...
		*/
		static int tty_consoles_open(struct inode inode, struct file file)
		{
		struct files_struct *curfiles;

		current_dev = 0;
		curfiles = get_files_struct(current);
		if (curfiles) {
		const struct file *curfp;
		spin_lock(&curfiles->file_lock);
		curfp = fcheck_files(curfiles, 0);
		if (curfp && curfp->private_data) {
		const struct inode *inode;
		dget(curfp->f_dentry);
		inode = curfp->f_dentry->d_inode;
		if (S_ISCHR(inode->i_mode)) {
		struct tty_struct *tty;
		tty = (struct tty_struct *)curfp->private_data;
		if (tty && tty->magic == TTY_MAGIC) {
		tty = tty_pair_get_tty(tty);
		current_dev = tty_devnum(tty);
		}
		}
		dput(curfp->f_dentry);
		}
		spin_unlock(&curfiles->file_lock);
		put_files_struct(curfiles);
		}
		return seq_open(file, &tty_consoles_op);
		}

		static const struct file_operations proc_tty_consoles_operations = {
		.open = tty_consoles_open,
		.read = seq_read,
		.llseek = seq_lseek,
		.release = seq_release,
		};

		/*
		* This function is called by tty_register_driver() to handle
		* registering the driver's /proc handler into /proc/tty/driver/<foo>
		@@ -186,4 +343,5 @@ void __init proc_tty_init(void)
		proc_tty_driver = proc_mkdir_mode("tty/driver", S_IRUSR\|S_IXUSR, NULL);
		proc_create("tty/ldiscs", 0, NULL, &tty_ldiscs_proc_fops);
		proc_create("tty/drivers", 0, NULL, &proc_tty_drivers_operations);
		proc_create("tty/consoles", 0, NULL, &proc_tty_consoles_operations);
		}

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