Now that the core vt code knows how to preserve unicode values for each
displayed character, it is then possible to let user space access it via
/dev/vcs*.
Unicode characters are presented as 32 bit values in native endianity
via the /dev/vcsu* devices, mimicking the simple /dev/vcs* devices.
Unicode with attributes (similarly to /dev/vcsa*) is not supported at
the moment.
Data is available only as long as the console is in UTF-8 mode. ENODATA
is returned otherwise.
This was tested with the latest development version (to become
version 5.7) of BRLTTY. Amongst other things, this allows ⠋⠕⠗ ⠞⠓⠊⠎
⠃⠗⠁⠊⠇⠇⠑⠀⠞⠑⠭⠞⠀to appear directly on braille displays regardless of the
console font being used.
Signed-off-by: Nicolas Pitre
Tested-by: Dave Mielke
Acked-by: Adam Borowski
---
drivers/tty/vt/vc_screen.c | 89 --
drivers/tty/vt/vt.c| 61 ++
include/linux/selection.h | 5 +++
3 files changed, 141 insertions(+), 14 deletions(-)
diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c
index e4a66e1fd0..9c44252e52 100644
--- a/drivers/tty/vt/vc_screen.c
+++ b/drivers/tty/vt/vc_screen.c
@@ -10,6 +10,12 @@
* Attribute/character pair is in native endianity.
*[minor: N+128]
*
+ * /dev/vcsuN: similar to /dev/vcsaN but using 4-byte unicode values
+ * instead of 1-byte screen glyph values.
+ *[minor: N+64]
+ *
+ * /dev/vcsuaN: same idea as /dev/vcsaN for unicode (not yet implemented).
+ *
* This replaces screendump and part of selection, so that the system
* administrator can control access using file system permissions.
*
@@ -51,6 +57,26 @@
#define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
+/*
+ * Our minor space:
+ *
+ * 0 ... 63 glyph mode without attributes
+ * 64 ... 127 unicode mode without attributes
+ * 128 ... 191 glyph mode with attributes
+ * 192 ... 255 unused (reserved for unicode with attributes)
+ *
+ * This relies on MAX_NR_CONSOLES being <= 63, meaning 63 actual consoles
+ * with minors 0, 64, 128 and 192 being proxies for the foreground console.
+ */
+#if MAX_NR_CONSOLES > 63
+#warning "/dev/vcs* devices may not accommodate more than 63 consoles"
+#endif
+
+#define console(inode) (iminor(inode) & 63)
+#define use_unicode(inode) (iminor(inode) & 64)
+#define use_attributes(inode) (iminor(inode) & 128)
+
+
struct vcs_poll_data {
struct notifier_block notifier;
unsigned int cons_num;
@@ -102,7 +128,7 @@ vcs_poll_data_get(struct file *file)
poll = kzalloc(sizeof(*poll), GFP_KERNEL);
if (!poll)
return NULL;
- poll->cons_num = iminor(file_inode(file)) & 127;
+ poll->cons_num = console(file_inode(file));
init_waitqueue_head(&poll->waitq);
poll->notifier.notifier_call = vcs_notifier;
if (register_vt_notifier(&poll->notifier) != 0) {
@@ -140,7 +166,7 @@ vcs_poll_data_get(struct file *file)
static struct vc_data*
vcs_vc(struct inode *inode, int *viewed)
{
- unsigned int currcons = iminor(inode) & 127;
+ unsigned int currcons = console(inode);
WARN_CONSOLE_UNLOCKED();
@@ -164,7 +190,6 @@ static int
vcs_size(struct inode *inode)
{
int size;
- int minor = iminor(inode);
struct vc_data *vc;
WARN_CONSOLE_UNLOCKED();
@@ -175,8 +200,12 @@ vcs_size(struct inode *inode)
size = vc->vc_rows * vc->vc_cols;
- if (minor & 128)
+ if (use_attributes(inode)) {
+ if (use_unicode(inode))
+ return -EOPNOTSUPP;
size = 2*size + HEADER_SIZE;
+ } else if (use_unicode(inode))
+ size *= 4;
return size;
}
@@ -197,12 +226,10 @@ static ssize_t
vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
struct inode *inode = file_inode(file);
- unsigned int currcons = iminor(inode);
struct vc_data *vc;
struct vcs_poll_data *poll;
- long pos;
- long attr, read;
- int col, maxcol, viewed;
+ long pos, read;
+ int attr, uni_mode, row, col, maxcol, viewed;
unsigned short *org = NULL;
ssize_t ret;
char *con_buf;
@@ -218,7 +245,8 @@ vcs_read(struct file *file, char __user *buf, size_t count,
loff_t *ppos)
*/
console_lock();
- attr = (currcons & 128);
+ uni_mode = use_unicode(inode);
+ attr = use_attributes(inode);
ret = -ENXIO;
vc = vcs_vc(inode, &viewed);
if (!vc)
@@ -227,6 +255,10 @@ vcs_read(struct file *file, char __user *buf, size_t
count, loff_t *ppos)
ret = -EINVAL;
if (pos < 0)
goto unlock_out;
+ /* we enforce 32-bit alignment for pos and count in unicode mode */
+ if (uni_mode && (pos | count) & 3)
+ goto unlock_out;
+
poll = file->private_data;
if (count && poll)
poll->seen_last_update
