I've completed my changes on the serial-u16550 driver. I have implemented most of your suggestions to my previous patch. Now:
* There is a user selectable flag "droponfull". Set to 1 and
any new bytes delivered to the driver after the buffer fills
up will be discarded until the buffer is able to flush some
bytes.
* If droponfull==0 (or is not set, the default is 0), the driver
proceeds to block further input by not calling snd_rawmidi_transmit_ack() and aborting the attempt. It will
try again later.
* I've redone a bit of the interface for the buffer routines. This was done to support the proper blocking/non-blocking methods
as spelled out above, and to try to protect the buffer data a bit.
So, if droponfull==0, we operate as originally desired (but the original implementation was broken a bit and this fixes it). If
droponfull==1 we now discard new bytes if our buffer is full; this
behavior fixes the driver "hang" problem we were having.
The changes should have no material effect on the "SNDRV_SERIAL_MS124W_MB"
device, and all others should still work well, though we can only
test with the SNDRV_SERIAL_GENERIC.
Please commit this at your earliest opportunity.
Thanks, - Steve
----------------
Change log entry: Fixes problem where buffers fill up with SNDRV_SERIAL_GENERIC
adaptor
when device doesn't signal CTS by dropping new bytes if the module
parameter "droponfull" == 1.
Index: serial-u16550.c =================================================================== RCS file: /cvsroot/alsa/alsa-kernel/drivers/serial-u16550.c,v retrieving revision 1.22 diff -u -p -r1.22 serial-u16550.c --- serial-u16550.c 14 Oct 2003 13:08:13 -0000 1.22 +++ serial-u16550.c 3 Dec 2003 01:14:42 -0000 @@ -63,6 +63,9 @@ static char *adaptor_names[] = { "Generic" };
+#define SNDRV_SERIAL_NORMALBUFF 0 /* Normal blocking buffer operation */
+#define SNDRV_SERIAL_DROPBUFF 1 /* Non-blocking discard operation */
+
static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX; /* Index 0-MAX */
static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR; /* ID for this card */
static int enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE; /* Enable this card */
@@ -73,6 +76,7 @@ static int base[SNDRV_CARDS] = {[0 ... (
static int outs[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 1}; /* 1 to 16 */
static int ins[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 1}; /* 1 to 16 */
static int adaptor[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] =
SNDRV_SERIAL_SOUNDCANVAS};
+static int droponfull[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS -1)] =
SNDRV_SERIAL_NORMALBUFF };MODULE_PARM(index, "1-" __MODULE_STRING(SNDRV_CARDS) "i"); MODULE_PARM_DESC(index, "Index value for Serial MIDI."); @@ -99,6 +103,9 @@ MODULE_PARM(outs, "1-" __MODULE_STRING(S MODULE_PARM_DESC(outs, "Number of MIDI outputs."); MODULE_PARM(ins, "1-" __MODULE_STRING(SNDRV_CARDS) "i"); MODULE_PARM_DESC(ins, "Number of MIDI inputs."); +MODULE_PARM(droponfull, "1-" __MODULE_STRING(SNDRV_CARDS) "i"); +MODULE_PARM_DESC(droponfull, "Flag to enable drop-on-full buffer mode"); +MODULE_PARM_SYNTAX(droponfull, SNDRV_ENABLED "," SNDRV_BOOLEAN_FALSE_DESC);
MODULE_PARM_SYNTAX(outs, SNDRV_ENABLED ",allows:{{1,16}},dialog:list");
MODULE_PARM_SYNTAX(ins, SNDRV_ENABLED ",allows:{{1,16}},dialog:list");
@@ -163,6 +170,7 @@ typedef struct _snd_uart16550 {
int buff_in_count;
int buff_in;
int buff_out;
+ int drop_on_full; // wait timer
unsigned int timer_running:1;
@@ -194,12 +202,15 @@ inline static void snd_uart16550_del_tim
inline static void snd_uart16550_buffer_output(snd_uart16550_t *uart)
{
unsigned short buff_out = uart->buff_out;
- outb(uart->tx_buff[buff_out], uart->base + UART_TX);
- uart->fifo_count++;
- buff_out++;
- buff_out &= TX_BUFF_MASK;
- uart->buff_out = buff_out;
- uart->buff_in_count--;
+ if( uart->buff_in_count > 0 )
+ {
+ outb(uart->tx_buff[buff_out], uart->base + UART_TX);
+ uart->fifo_count++;
+ buff_out++;
+ buff_out &= TX_BUFF_MASK;
+ uart->buff_out = buff_out;
+ uart->buff_in_count--;
+ }
}/* This loop should be called with interrupts disabled
@@ -257,9 +268,12 @@ static void snd_uart16550_io_loop(snd_ua
|| uart->adaptor == SNDRV_SERIAL_GENERIC) {
/* Can't use FIFO, must send only when CTS is true */
status = inb(uart->base + UART_MSR);
- if (uart->fifo_count == 0 && (status & UART_MSR_CTS)
- && uart->buff_in_count > 0)
- snd_uart16550_buffer_output(uart);
+ while( (uart->fifo_count == 0) && (status & UART_MSR_CTS) &&
+ (uart->buff_in_count > 0) )
+ {
+ snd_uart16550_buffer_output(uart);
+ status = inb( uart->base + UART_MSR );
+ }
} else {
/* Write loop */
while (uart->fifo_count < uart->fifo_limit /* Can we write ? */
@@ -576,19 +590,33 @@ static int snd_uart16550_output_close(sn
return 0;
};-inline static void snd_uart16550_write_buffer(snd_uart16550_t *uart, unsigned char
byte)
+inline static int snd_uart16550_buffer_can_write( snd_uart16550_t *uart, int Num )
{
- unsigned short buff_in = uart->buff_in;
- uart->tx_buff[buff_in] = byte;
- buff_in++;
- buff_in &= TX_BUFF_MASK;
- uart->buff_in = buff_in;
- uart->buff_in_count++;
- if (uart->irq < 0) /* polling mode */
- snd_uart16550_add_timer(uart);
+ if( uart->buff_in_count + Num < TX_BUFF_SIZE )
+ return 1;
+ else
+ return 0;
}-static void snd_uart16550_output_byte(snd_uart16550_t *uart, snd_rawmidi_substream_t
* substream, unsigned char midi_byte)
+inline static int snd_uart16550_write_buffer(snd_uart16550_t *uart, unsigned char
byte)
+{
+ unsigned short buff_in = uart->buff_in;
+ if( uart->buff_in_count < TX_BUFF_SIZE )
+ {
+ uart->tx_buff[buff_in] = byte;
+ buff_in++;
+ buff_in &= TX_BUFF_MASK;
+ uart->buff_in = buff_in;
+ uart->buff_in_count++;
+ if (uart->irq < 0) /* polling mode */
+ snd_uart16550_add_timer(uart);
+ return 1;
+ }
+ else
+ return 0;
+}
+
+static int snd_uart16550_output_byte(snd_uart16550_t *uart, snd_rawmidi_substream_t *
substream, unsigned char midi_byte)
{
if (uart->buff_in_count == 0 /* Buffer empty? */
&& ((uart->adaptor != SNDRV_SERIAL_MS124W_SA &&
@@ -611,13 +639,14 @@ static void snd_uart16550_output_byte(sn
}
}
} else {
- if (uart->buff_in_count >= TX_BUFF_SIZE) {
+ if( !snd_uart16550_write_buffer(uart, midi_byte) ) {
snd_printk("%s: Buffer overrun on device at 0x%lx\n",
uart->rmidi->name, uart->base);
- return;
+ return 0;
}
- snd_uart16550_write_buffer(uart, midi_byte);
}
+
+ return 1;
}static void snd_uart16550_output_write(snd_rawmidi_substream_t * substream)
@@ -661,40 +690,41 @@ static void snd_uart16550_output_write(s
}
} else {
first = 0;
- while (1) {
- if (snd_rawmidi_transmit(substream, &midi_byte, 1) != 1)
- break;
+ while( 1 == snd_rawmidi_transmit_peek(substream, &midi_byte, 1) )
+ {
/* Also send F5 after 3 seconds with no data to handle device
disconnect */
if (first == 0 && (uart->adaptor == SNDRV_SERIAL_SOUNDCANVAS ||
uart->adaptor == SNDRV_SERIAL_GENERIC) &&
(uart->prev_out != substream->number || jiffies-lasttime >
3*HZ)) {- /* We will need three bytes of data here (worst case).
*/
- if (uart->buff_in_count >= TX_BUFF_SIZE - 3)
- break;
-
- /* Roland Soundcanvas part selection */
- /* If this substream of the data is different previous
- substream in this uart, send the change part event
*/
- uart->prev_out = substream->number;
- /* change part */
- snd_uart16550_output_byte(uart, substream, 0xf5);
- /* data */
- snd_uart16550_output_byte(uart, substream,
uart->prev_out + 1);
- /* If midi_byte is a data byte, send the previous
status byte */
- if ((midi_byte < 0x80) && (uart->adaptor ==
SNDRV_SERIAL_SOUNDCANVAS))
- snd_uart16550_output_byte(uart, substream,
uart->prev_status[uart->prev_out]);
- }
+ if( snd_uart16550_buffer_can_write( uart, 3 ) )
+ {
+ /* Roland Soundcanvas part selection */
+ /* If this substream of the data is different
previous
+ substream in this uart, send the change part
event */
+ uart->prev_out = substream->number;
+ /* change part */
+ snd_uart16550_output_byte(uart, substream,
0xf5);
+ /* data */
+ snd_uart16550_output_byte(uart, substream,
uart->prev_out + 1);
+ /* If midi_byte is a data byte, send the
previous status byte */
+ if ((midi_byte < 0x80) && (uart->adaptor ==
SNDRV_SERIAL_SOUNDCANVAS))
+ snd_uart16550_output_byte(uart, substream,
uart->prev_status[uart->prev_out]);
+ }
+ else if( !uart->drop_on_full )
+ break;- /* buffer full? */ - if (uart->buff_in_count >= TX_BUFF_SIZE) - break; + }
/* send midi byte */
- snd_uart16550_output_byte(uart, substream, midi_byte);
+ if( !snd_uart16550_output_byte(uart, substream, midi_byte) &&
!uart->drop_on_full )
+ break;
+
if (midi_byte >= 0x80 && midi_byte < 0xf0)
uart->prev_status[uart->prev_out] = midi_byte;
first = 1;
+
+ snd_rawmidi_transmit_ack( substream, 1 );
}
lasttime = jiffies;
}
@@ -755,6 +785,7 @@ static int __init snd_uart16550_create(s
unsigned int speed,
unsigned int base,
int adaptor,
+ int droponfull,
snd_uart16550_t **ruart)
{
static snd_device_ops_t ops = {
@@ -771,6 +802,7 @@ static int __init snd_uart16550_create(s
spin_lock_init(&uart->open_lock);
uart->irq = -1;
uart->base = iobase;
+ uart->drop_on_full = droponfull; if ((err = snd_uart16550_detect(uart)) <= 0) {
printk(KERN_ERR "no UART detected at 0x%lx\n", iobase);
@@ -900,6 +932,7 @@ static int __init snd_serial_probe(int d
speed[dev],
base[dev],
adaptor[dev],
+ droponfull[dev],
&uart)) < 0) {
snd_card_free(card);
return err;
@@ -910,7 +943,7 @@ static int __init snd_serial_probe(int d
return err;
}- sprintf(card->longname, "%s at 0x%lx, irq %d speed %d div %d outs %d ins %d adaptor
%s",
+ sprintf(card->longname, "%s at 0x%lx, irq %d speed %d div %d outs %d ins %d adaptor
%s droponfull %d",
card->shortname,
uart->base,
uart->irq,
@@ -918,7 +951,8 @@ static int __init snd_serial_probe(int d
(int)uart->divisor,
outs[dev],
ins[dev],
- adaptor_names[uart->adaptor]);
+ adaptor_names[uart->adaptor],
+ uart->drop_on_full); if ((err = snd_card_register(card)) < 0) {
snd_card_free(card);
@@ -964,7 +998,7 @@ module_exit(alsa_card_serial_exit)/* format is: snd-serial=enable,index,id,
port,irq,speed,base,outs,
- ins,adaptor */
+ ins,adaptor,droponfull */static int __init alsa_card_serial_setup(char *str)
{
@@ -981,7 +1015,8 @@ static int __init alsa_card_serial_setup
get_option(&str,&base[nr_dev]) == 2 &&
get_option(&str,&outs[nr_dev]) == 2 &&
get_option(&str,&ins[nr_dev]) == 2 &&
- get_option(&str,&adaptor[nr_dev]) == 2);
+ get_option(&str,&adaptor[nr_dev]) == 2 &&
+ get_option(&str,&droponfull[nr_dev]) == 2 );
nr_dev++;
return 1;
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