tty: n_gsm: replace use of gsm_read_ea() with gsm_read_ea_val()

Replace the use of gsm_read_ea() with gsm_read_ea_val() where applicable to
improve code readability and avoid errors like in the past. See first link
below for reference.

Link: https://lore.kernel.org/all/20220504081733.3494-1-daniel.starke@siemens.com/
Link: https://lore.kernel.org/all/202208222147.WfFRmf1r-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220831073800.7459-3-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 2508498..c5445d3 100644 (file)
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1415,18 +1415,12 @@ static void gsm_control_modem(struct gsm_mux *gsm, const u8 *data, int clen)
        unsigned int modem = 0;
        struct gsm_dlci *dlci;
        int len = clen;
-       int slen;
+       int cl = clen;
        const u8 *dp = data;
        struct tty_struct *tty;
 
-       while (gsm_read_ea(&addr, *dp++) == 0) {
-               len--;
-               if (len == 0)
-                       return;
-       }
-       /* Must be at least one byte following the EA */
-       len--;
-       if (len <= 0)
+       len = gsm_read_ea_val(&addr, data, cl);
+       if (len < 1)
                return;
 
        addr >>= 1;
@@ -1435,15 +1429,20 @@ static void gsm_control_modem(struct gsm_mux *gsm, const u8 *data, int clen)
                return;
        dlci = gsm->dlci[addr];
 
-       slen = len;
-       while (gsm_read_ea(&modem, *dp++) == 0) {
-               len--;
-               if (len == 0)
-                       return;
-       }
-       len--;
+       /* Must be at least one byte following the EA */
+       if ((cl - len) < 1)
+               return;
+
+       dp += len;
+       cl -= len;
+
+       /* get the modem status */
+       len = gsm_read_ea_val(&modem, dp, cl);
+       if (len < 1)
+               return;
+
        tty = tty_port_tty_get(&dlci->port);
-       gsm_process_modem(tty, dlci, modem, slen - len);
+       gsm_process_modem(tty, dlci, modem, cl);
        if (tty) {
                tty_wakeup(tty);
                tty_kref_put(tty);
@@ -1918,11 +1917,10 @@ static void gsm_dlci_data(struct gsm_dlci *dlci, const u8 *data, int clen)
        struct tty_port *port = &dlci->port;
        struct tty_struct *tty;
        unsigned int modem = 0;
-       int len = clen;
-       int slen = 0;
+       int len;
 
        if (debug & 16)
-               pr_debug("%d bytes for tty\n", len);
+               pr_debug("%d bytes for tty\n", clen);
        switch (dlci->adaption)  {
        /* Unsupported types */
        case 4:         /* Packetised interruptible data */
@@ -1930,24 +1928,22 @@ static void gsm_dlci_data(struct gsm_dlci *dlci, const u8 *data, int clen)
        case 3:         /* Packetised uininterruptible voice/data */
                break;
        case 2:         /* Asynchronous serial with line state in each frame */
-               while (gsm_read_ea(&modem, *data++) == 0) {
-                       len--;
-                       slen++;
-                       if (len == 0)
-                               return;
-               }
-               len--;
-               slen++;
+               len = gsm_read_ea_val(&modem, data, clen);
+               if (len < 1)
+                       return;
                tty = tty_port_tty_get(port);
                if (tty) {
-                       gsm_process_modem(tty, dlci, modem, slen);
+                       gsm_process_modem(tty, dlci, modem, len);
                        tty_wakeup(tty);
                        tty_kref_put(tty);
                }
+               /* Skip processed modem data */
+               data += len;
+               clen -= len;
                fallthrough;
        case 1:         /* Line state will go via DLCI 0 controls only */
        default:
-               tty_insert_flip_string(port, data, len);
+               tty_insert_flip_string(port, data, clen);
                tty_flip_buffer_push(port);
        }
 }
@@ -1968,24 +1964,27 @@ static void gsm_dlci_command(struct gsm_dlci *dlci, const u8 *data, int len)
 {
        /* See what command is involved */
        unsigned int command = 0;
-       while (len-- > 0) {
-               if (gsm_read_ea(&command, *data++) == 1) {
-                       int clen = *data++;
-                       len--;
-                       /* FIXME: this is properly an EA */
-                       clen >>= 1;
-                       /* Malformed command ? */
-                       if (clen > len)
-                               return;
-                       if (command & 1)
-                               gsm_control_message(dlci->gsm, command,
-                                                               data, clen);
-                       else
-                               gsm_control_response(dlci->gsm, command,
-                                                               data, clen);
-                       return;
-               }
-       }
+       unsigned int clen = 0;
+       unsigned int dlen;
+
+       /* read the command */
+       dlen = gsm_read_ea_val(&command, data, len);
+       len -= dlen;
+       data += dlen;
+
+       /* read any control data */
+       dlen = gsm_read_ea_val(&clen, data, len);
+       len -= dlen;
+       data += dlen;
+
+       /* Malformed command? */
+       if (clen > len)
+               return;
+
+       if (command & 1)
+               gsm_control_message(dlci->gsm, command, data, clen);
+       else
+               gsm_control_response(dlci->gsm, command, data, clen);
 }
 
 /**