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[PATCH] dz: Handle special conditions on reception correctly

To: Andrew Morton <akpm@linux-foundation.org>
Subject: [PATCH] dz: Handle special conditions on reception correctly
From: "Maciej W. Rozycki" <macro@linux-mips.org>
Date: Fri, 19 Oct 2007 21:51:08 +0100 (BST)
Cc: linux-mips@linux-mips.org, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
 Handle the read and ignore status masks correctly.  Handle the BREAK 
condition as expected: a framing error with a null character is a BREAK, 
any other framing error is a framing error indeed.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
---
 Tested with checkpatch.pl and at the run-time -- MIPS/Linux on a 
DECstation 5000/200.

 Please apply,

  Maciej

patch-mips-2.6.23-rc5-20070904-dz-receive-8
diff -up --recursive --new-file 
linux-mips-2.6.23-rc5-20070904.macro/drivers/serial/dz.c 
linux-mips-2.6.23-rc5-20070904/drivers/serial/dz.c
--- linux-mips-2.6.23-rc5-20070904.macro/drivers/serial/dz.c    2007-05-02 
04:56:10.000000000 +0000
+++ linux-mips-2.6.23-rc5-20070904/drivers/serial/dz.c  2007-10-13 
22:24:40.000000000 +0000
@@ -172,6 +172,7 @@ static void dz_enable_ms(struct uart_por
  */
 static inline void dz_receive_chars(struct dz_port *dport_in)
 {
+       struct uart_port *uport;
        struct dz_port *dport;
        struct tty_struct *tty = NULL;
        struct uart_icount *icount;
@@ -182,57 +183,56 @@ static inline void dz_receive_chars(stru
 
        while ((status = dz_in(dport_in, DZ_RBUF)) & DZ_DVAL) {
                dport = &dz_ports[LINE(status)];
-               tty = dport->port.info->tty;    /* point to the proper dev */
+               uport = &dport->port;
+               tty = uport->info->tty;         /* point to the proper dev */
 
                ch = UCHAR(status);             /* grab the char */
+               flag = TTY_NORMAL;
 
-               icount = &dport->port.icount;
+               icount = &uport->icount;
                icount->rx++;
 
-               flag = TTY_NORMAL;
-               if (status & DZ_FERR) {         /* frame error */
+               if (unlikely(status & (DZ_OERR | DZ_FERR | DZ_PERR))) {
+
                        /*
-                        * There is no separate BREAK status bit, so
-                        * treat framing errors as BREAKs for Magic SysRq
-                        * and SAK; normally, otherwise.
+                        * There is no separate BREAK status bit, so treat
+                        * null characters with framing errors as BREAKs;
+                        * normally, otherwise.  For this move the Framing
+                        * Error bit to a simulated BREAK bit.
                         */
-                       if (uart_handle_break(&dport->port))
-                               continue;
-                       if (dport->port.flags & UPF_SAK)
+                       if (!ch) {
+                               status |= (status & DZ_FERR) >>
+                                         (ffs(DZ_FERR) - ffs(DZ_BREAK));
+                               status &= ~DZ_FERR;
+                       }
+
+                       /* Handle SysRq/SAK & keep track of the statistics. */
+                       if (status & DZ_BREAK) {
+                               icount->brk++;
+                               if (uart_handle_break(uport))
+                                       continue;
+                       } else if (status & DZ_FERR)
+                               icount->frame++;
+                       else if (status & DZ_PERR)
+                               icount->parity++;
+                       if (status & DZ_OERR)
+                               icount->overrun++;
+
+                       status &= uport->read_status_mask;
+                       if (status & DZ_BREAK)
                                flag = TTY_BREAK;
-                       else
+                       else if (status & DZ_FERR)
                                flag = TTY_FRAME;
-               } else if (status & DZ_OERR)    /* overrun error */
-                       flag = TTY_OVERRUN;
-               else if (status & DZ_PERR)      /* parity error */
-                       flag = TTY_PARITY;
-
-               /* keep track of the statistics */
-               switch (flag) {
-               case TTY_FRAME:
-                       icount->frame++;
-                       break;
-               case TTY_PARITY:
-                       icount->parity++;
-                       break;
-               case TTY_OVERRUN:
-                       icount->overrun++;
-                       break;
-               case TTY_BREAK:
-                       icount->brk++;
-                       break;
-               default:
-                       break;
+                       else if (status & DZ_PERR)
+                               flag = TTY_PARITY;
+
                }
 
-               if (uart_handle_sysrq_char(&dport->port, ch))
+               if (uart_handle_sysrq_char(uport, ch))
                        continue;
 
-               if ((status & dport->port.ignore_status_mask) == 0) {
-                       uart_insert_char(&dport->port,
-                                        status, DZ_OERR, ch, flag);
-                       lines_rx[LINE(status)] = 1;
-               }
+               uart_insert_char(uport, status, DZ_OERR, ch, flag);
+               lines_rx[LINE(status)] = 1;
        }
        for (i = 0; i < DZ_NB_PORT; i++)
                if (lines_rx[i])
@@ -552,11 +552,17 @@ static void dz_set_termios(struct uart_p
        dport->port.read_status_mask = DZ_OERR;
        if (termios->c_iflag & INPCK)
                dport->port.read_status_mask |= DZ_FERR | DZ_PERR;
+       if (termios->c_iflag & (BRKINT | PARMRK))
+               dport->port.read_status_mask |= DZ_BREAK;
 
        /* characters to ignore */
        uport->ignore_status_mask = 0;
+       if ((termios->c_iflag & (IGNPAR | IGNBRK)) == (IGNPAR | IGNBRK))
+               dport->port.ignore_status_mask |= DZ_OERR;
        if (termios->c_iflag & IGNPAR)
                dport->port.ignore_status_mask |= DZ_FERR | DZ_PERR;
+       if (termios->c_iflag & IGNBRK)
+               dport->port.ignore_status_mask |= DZ_BREAK;
 
        spin_unlock_irqrestore(&dport->port.lock, flags);
 }
diff -up --recursive --new-file 
linux-mips-2.6.23-rc5-20070904.macro/drivers/serial/dz.h 
linux-mips-2.6.23-rc5-20070904/drivers/serial/dz.h
--- linux-mips-2.6.23-rc5-20070904.macro/drivers/serial/dz.h    2007-02-05 
16:38:50.000000000 +0000
+++ linux-mips-2.6.23-rc5-20070904/drivers/serial/dz.h  2007-09-08 
12:20:40.000000000 +0000
@@ -33,6 +33,8 @@
 #define DZ_FERR        0x2000                 /* Frame error indicator */
 #define DZ_PERR        0x1000                 /* Parity error indicator */
 
+#define DZ_BREAK       0x0800                 /* BREAK event software flag */
+
 #define LINE(x) ((x & DZ_LINE_MASK) >> 8)     /* Get the line number
                                                  from the input buffer */
 #define UCHAR(x) ((unsigned char)(x & DZ_RBUF_MASK))

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