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Code Issues Releases Activity

Change dev_read to use per-process data.

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This commit is contained in:
Robin Mallinson 2012-11-18 21:12:36 +00:00
parent 38101f8a62
commit e993a088eb
1 changed files with 55 additions and 49 deletions
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104
ServoBlaster/servoblaster.c
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@ -316,31 +316,32 @@ void cleanup_module(void)
unregister_chrdev_region(devno, 1);
}
// This stores the /dev/servoblaster content for a given user process.
struct userReturnedData {
int idx;
char returnedData[NUM_SERVOS * 10];
};
// This struct is used to store all temporary data required per process
// which reads/writes the device file.
struct process_data
{
// Stores the /dev/servoblaster content for a given user process.
// Allowing 10 chars per line.
int ret_idx;
char ret_data[NUM_SERVOS * 10];
// This stores one user command (single line) for a given user process.
// e.g. "3=180"
// Line length is expected to be <32
struct userCommandData {
int idx;
char commandData[32];
// Stores one user command (single line) for a given user process.
// e.g. "3=180"
// Line length is expected to be <32
int cmd_idx;
char cmd_data[32];
};
// kmalloc the temporary data required for each user:
// *returnedData string for dev_read
// *useCommand buffer for dev_write to allow incremental writing of data.
static int dev_open(struct inode *inod,struct file *fil)
{
fil->private_data = kmalloc( 32, GFP_KERNEL );
fil->private_data = kmalloc( sizeof(struct process_data), GFP_KERNEL );
if (0 == fil->private_data)
{
printk(KERN_WARNING "ServoBlaster: Failed to allocate user data\n");
return -ENOMEM;
}
memset(fil->private_data, 0, sizeof(struct process_data));
return 0;
}
@ -351,47 +352,52 @@ static int written_data[NUM_SERVOS] = { 0 };
static ssize_t dev_read(struct file *filp,char *buf,size_t count,loff_t *f_pos)
{
ssize_t bytesPrinted = 0;
int servo;
static int idx=0;
// Allow 10 chars per line:
static char returnedData[NUM_SERVOS * 10] = {0};
struct process_data* const pdata = filp->private_data;
if (0 == *f_pos)
// Only proceed if we have private data, else return EOF.
if (0 != pdata)
{
// Get fresh data
for (servo=0, idx=0; servo < NUM_SERVOS; ++servo)
int servo;
int* const idx = &(pdata->ret_idx);
char* const returnedData = pdata->ret_data;
if (0 == *f_pos)
{
idx += snprintf(returnedData+idx, sizeof(returnedData)-idx,
"%i %i\n",
servo,
written_data[servo]
);
// Get fresh data
for (servo=0, *idx=0; servo < NUM_SERVOS; ++servo)
{
*idx += snprintf(returnedData+*idx, sizeof(pdata->ret_data)-*idx,
"%i %i\n",
servo,
written_data[servo]
);
}
}
}
if (*f_pos >= idx)
{
//EOF
bytesPrinted=0;
}
else if ( (*f_pos + count) < idx )
{
// Sufficient data to fulfil request
if (copy_to_user(buf,returnedData+*f_pos,count)) {
return -EFAULT;
if (*f_pos >= *idx)
{
//EOF
bytesPrinted=0;
}
else if ( (*f_pos + count) < *idx )
{
// Sufficient data to fulfil request
if (copy_to_user(buf,returnedData+*f_pos,count)) {
return -EFAULT;
}
*f_pos+=count;
bytesPrinted=count;
}
else
{
// Return all the data we have
const int nBytes = *idx-*f_pos;
if (copy_to_user(buf,returnedData+*f_pos, nBytes)) {
return -EFAULT;
}
*f_pos+=nBytes;
bytesPrinted=nBytes;
}
*f_pos+=count;
bytesPrinted=count;
}
else
{
// Return all the data we have
const int nBytes = idx-*f_pos;
if (copy_to_user(buf,returnedData+*f_pos, nBytes)) {
return -EFAULT;
}
*f_pos+=nBytes;
bytesPrinted=nBytes;
}
return bytesPrinted;
}