I have a task to write a block device driver (/dev/dua - for example) , this block device is must be looks like to OS as a disk device like /dev/sda. So, this driver must process data blocks and write it to other block device.
I looking for a right way to performs I/O operations on the backend device like "/dev/sdb".
I have played with the vfs_read/write routines it's works at glance for disk sector sized transfers. But, probably there is more effective way to performs I/O on backend device ?
TIA.
Follows a piece of code (original has been found here : https://github.com/asimkadav/block-filter) implements a "filtering" feature, so it can be used as a method to performs I/O on a backend block device `
void misc_request_fn(struct request_queue *q, struct bio *bio) {
printk ("we are passing bios.\n");
// here is where we trace requests...
original_request_fn (q, bio);
return;
}
void register_block_device(char *path) {
struct request_queue *blkdev_queue = NULL;
if (path == NULL) {
printk ("Block device empty.\n");
return;
}
printk ("Will open %s.\n", path);
blkdev = lookup_bdev(path);
if (IS_ERR(blkdev)) {
printk ("No such block device.\n");
return;
}
printk ("Found block device %p with bs %d.\n", blkdev, blkdev->bd_block_size);
blkdev_queue = bdev_get_queue(blkdev);
original_request_fn = blkdev_queue->request_fn;
blkdev_queue->request_fn = misc_request_fn;
}
`
Related
I'm working on an application where I process commands of fixed length received via UART.
I'm also using FreeRTOS and the task that handles the incoming commands is suspended until the uart interrupt handler is called, so my code is like this
void USART1_IRQHandler()
{
HAL_UART_IRQHandler(&huart1);
}
void HAL_UART_ErrorCallback(UART_HandleTypeDef *huart){
HAL_UART_Receive_IT(&huart1, uart_rx_buf, CMD_LEN);
}
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart){
BaseType_t higherTaskReady = pdFALSE;
HAL_UART_Receive_IT(&huart1, uart_rx_buf, CMD_LEN); //restart interrupt handler
xSemaphoreGiveFromISR(uart_mutex, &higherTaskReady);
portYIELD_FROM_ISR( higherTaskReady); //Relase the semaphore
}
I am using the ErrorCallBack in case if an overflow occurs. Now I successfully catch every correct command, even if they are issued char by char.
However, I'm trying to make the system more error-proof by considering the case where more characters are received than expected.
The command length is 4 but if I receive, for example, 5 chars, then the first 4 is processed normally but when another command is received it starts from the last unprocessed char, so another 3 chars are needed until I can correctly process the commands again.
Luckily, the ErrorCallback is called whenever I receive more than 4 chars, so I know when it happens, but I need a robust way of cleaning the UART buffer so the previous chars are gone.
One solution I can think of is using UART receive 1 char at a time until it can't receive anymore, but is there a better way to simply flush the buffer?
Yes, the problem is the lack of delimiter, because every byte can can carry a value to be processed from 0 to 255. So, how can you detect the inconsistency?
My solution is a checksum byte in the protocol. If the checksum fails, a blocking-mode UART_Receive function is called in order to put the rest of the data from the "system-buffer" to a "disposable-buffer". In my example the fix size of the protocol is 6, I use the UART6 and I have a global variable RxBuffer. Here is the code:
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *UartHandle)
{
if(UartHandle->Instance==USART6) {
if(your_checksum_is_ok) {
// You can process the incoming data
} else {
char TempBuffer;
HAL_StatusTypeDef hal_status;
do {
hal_status = HAL_UART_Receive(&huart6, (uint8_t*)&TempBuffer, 1, 10);
} while(hal_status != HAL_TIMEOUT);
}
HAL_UART_Receive_IT(&huart6, (uint8_t*)RxBuffer, 6);
}
}
void HAL_UART_ErrorCallback(UART_HandleTypeDef *UartHandle) {
if(UartHandle->Instance==USART6) {
HAL_UART_Receive_IT(&huart6, (uint8_t*)RxBuffer, 6);
}
}
I am trying to read data with unkown size using UART Receive Interrupt. In the call back function, I enabled Rx interrupt in order to read characters until \n is gotten. If \n is get, then higher priority task which is deferred interrupt handler is woken. The problem is that I tried to read one by one byte via call back function and I tried to put each character into a buffer, but unfortunately buffer could not get any character. Moreover, deferred interrupt handler could not be woken.
My STM32 board is STM32F767ZI, and my IDE is KEIL.
Some Important notes before sharing the code:
1. rxIndex and gpsBuffer are declared as global.
2. Periodic function works without any problem.
Here is my code:
Periodic Function, Priority = 1
void vPeriodicTask(void *pvParameters)
{
const TickType_t xDelay500ms = pdMS_TO_TICKS(500UL);
while (1) {
vTaskDelay(xDelay500ms);
HAL_UART_Transmit(&huart3,(uint8_t*)"Imu\r\n",sizeof("Imu\r\n"),1000);
HAL_GPIO_TogglePin(GPIOB,GPIO_PIN_7);
}
}
Deferred Interrupt, Priority = 3
void vHandlerTask(void *pvParameters)
{
const TickType_t xMaxExpectedBlockTime = pdMS_TO_TICKS(1000);
while(1) {
if (xSemaphoreTake(xBinarySemaphore,xMaxExpectedBlockTime) == pdPASS) {
HAL_UART_Transmit(&huart3,(uint8_t*)"Semaphore Acquired\r\n",sizeof("Semaphore
Acquired\r\n"),1000);
// Some important processes will be added here
rxIndex = 0;
HAL_GPIO_TogglePin(GPIOB,GPIO_PIN_14);
}
}
}
Call back function:
void HAL_UART_RxCptlCallBack(UART_HandleTypeDef *huart)
{
gpsBuffer[rxIndex++] = rData;
if (rData == 0x0A) {
BaseType_t xHigherPriorityTaskWoken;
xSemaphoreGiveFromISR(xBinarySemaphore,&xHigherPriorityTaskWoken);
portEND_SWITCHING_ISR(xHigherPriorityTaskWoken);
}
HAL_UART_Receive_IT(huart,(uint8_t*)&rData,1);
}
Main function
HAL_UART_Receive_IT(&huart3,&rData,1);
xBinarySemaphore = xSemaphoreCreateBinary();
if (xBinarySemaphore != NULL) {
//success
xTaskCreate(vHandlerTask,"Handler",128,NULL,1,&vHandlerTaskHandler);
xTaskCreate(vPeriodicTask,"Periodic",128,NULL,3,&vPeriodicTaskHandler);
vTaskStartScheduler();
}
Using HAL for it is a best way to get into the troubles. It uses HAL_Delay which is systick dependant and you should rewrite this function to read RTOS tick instead.
I use queues to pass the data (the references to data) but it should work. There is always a big question mark when using the HAL functions.
void HAL_UART_RxCptlCallBack(UART_HandleTypeDef *huart)
{
BaseType_t xHigherPriorityTaskWoken = pdFALSE;
gpsBuffer[rxIndex++] = rData;
if (rData == 0x0A) {
if(xSemaphoreGiveFromISR(xBinarySemaphore,&xHigherPriorityTaskWoken) == pdFALSE)
{
/* some error handling */
}
}
HAL_UART_Receive_IT(huart,(uint8_t*)&rData,1);
portEND_SWITCHING_ISR(xHigherPriorityTaskWoken);
}
Concluding if I use HAL & RTOS I always modify the way HAL handles timeouts.
I need to play sounds upon certain events, and want to minimize
processor load, because some image processing is being done too, and
processor performance is limited.
For the present, I play only one sound at a time, and I do it as
follows:
At program startup, sounds are read from .wav files
and the raw pcm data are loaded into memory
a sound device is opened (snd_pcm_open() in mode SND_PCM_NONBLOCK)
a worker thread is started which continously calls snd_pcm_writei()
as long as it is fed with data (data->remaining > 0).
Somewhat resumed, the worker thread function is
static void *Thread_Func (void *arg)
{
thrdata_t *data = (thrdata_t *)arg;
snd_pcm_sframes_t res;
while (1)
{ pthread_mutex_lock (&lock);
if (data->shall_stop)
{ data->shall_stop = false;
snd_pcm_drop (data->pcm_device);
snd_pcm_prepare (data->pcm_device);
data->remaining = 0;
}
if (data->remaining > 0)
{ res = snd_pcm_writei (data->pcm_device, data->bufptr, data->remaining);
if (res == -EAGAIN) continue;
if (res < 0) // error
{ fprintf (stderr, "snd_pcm_writeX() error: %s\n", snd_strerror(result));
snd_pcm_recover (data->sub_device, res);
}
else // another chunk has been handed over to sound hw
{ data->bufptr += res * bytes_per_frame;
data->remaining -= res;
}
if (data->remaining == 0) snd_pcm_prepare (data->pcm_device);
}
pthread_mutex_unlock (&lock);
usleep (sleep_us); // processor relief
}
} // Thread_Func
Ok, so this works well for one sound at a time. How do I play various?
I found dmix, but it seems a tool on user level, to mix streams coming
from separate programs.
Furthermore, I found the Simple Mixer Interface in the ALSA Project C
Library Interface, without any hint or example or tutorial about how
to use all these function described by one line of text each.
As a last resort I could calculate the mean value of all the buffers
to be played synchronously. So long I've been avoiding that, hoping
that an ALSA solution might use sound hardware resources, thus
relieving the main processor.
I'd be thankful for any hint about how to continue.
Hi I am writing a simple console app that needs to write bytes to MCP2210 USB to SPI Master
I found this library over here, seems to do good job with connecting the device and reading the metadata.
I am writing message to the board as below
public static byte[] Talk()
{
var device = DeviceList.Local.GetHidDevices(1240, 222).FirstOrDefault();
if (device == null)
{
Console.WriteLine($"Could not find a device with Vendor Id:1240, Product Id:222 ");
return null;
}
var reportDescriptor = device.GetReportDescriptor();
foreach (var deviceItem in reportDescriptor.DeviceItems)
{
Console.WriteLine("Opening device for 20 seconds...");
if (!device.TryOpen(out var hidStream))
{
Console.WriteLine("Failed to open device.");
continue;
}
Console.WriteLine("Opened device.");
hidStream.ReadTimeout = Timeout.Infinite;
hidStream.Write(new byte[3] {60, 00, 00});
}
Not sure If I am writing it correctly.
While writing I need to do a chip selection as displayed in this other terminal
Any help is greatly appreciated
Here is the MC I am using https://www.microchip.com/wwwproducts/en/MCP2210
I do not see a closing of your stream. This may cause your data to not even being sent (at least not in time).
Consider using blocks with streams.
But with out parameters not possible.
I'm using ST STM32F101xB and μC/OS-II, I was having external clock (HSE) on old board and it's running fine. We wanted to use internal clock (HSI) on new board, however, the RTOS (Appmaintask()) doesn't run using internal clock, i have changed my code as below, any idea what's wrong with the change:
void BSP_Init (void)
{
RCC_DeInit();
//RCC_HSEConfig(RCC_HSE_ON);
//RCC_WaitForHSEStartUp();
RCC_HCLKConfig(RCC_SYSCLK_Div1);
RCC_PCLK2Config(RCC_HCLK_Div1); // APB2 clock divide by 1 => 64MHz
RCC_PCLK1Config(RCC_HCLK_Div2); // APB1 clock divide by 2 => 32MHz
FLASH_SetLatency(FLASH_Latency_2);
FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
//RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_8); // 64MHz
RCC_PLLConfig(RCC_PLLSource_HSI_Div2, RCC_PLLMul_8);
RCC_PLLCmd(ENABLE);
RCC_LSEConfig(RCC_LSE_OFF);
while (RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET) {
;
}
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
while (RCC_GetSYSCLKSource() != 0x08) {
;
}
//Set the Vector Table base location at 0x08000000
//NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x0);
// Need to finalize and arange priority for each interrupts in future,
// So that 1 interrupt wont blocks another interrupt.
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_3);
}
void main()
{
INT8U err;
cpuObj = new Cstm32f10x();
BSP_Init();
BSP_IntDisAll(); /* Disable all ints until we are ready to accept them. */
OSInit();
err = OSTaskCreateExt (AppMainTask,
(void *)0,
(OS_STK *)&AppMainTaskStk[APP_MAIN_TASK_STK_SIZE-1],
APP_MAIN_TASK_PRIO,
APP_MAIN_TASK_ID,
(OS_STK *)&AppMainTaskStk[0],
APP_MAIN_TASK_STK_SIZE,
(void *)0,
OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR);
OSStart(); // Start multitasking (i.e. give control to uC/OS-II)
}
void AppMainTask (void *p_arg)
{
OS_CPU_SysTickInit();
while(TRUE)
{
OSTimeDly(1);
}
}
Thanks.
Setting up of the PLL is normally performed in the CMSIS start-up code provided by ST/ARM. This code executes as part of the runtime environment start-up before main() is called. I recommend that you use this code for chip initialisation since static data initialisation and static object constructors run before main() and will be running before possibly critical initialisation.
The CMSIS with Cortex-M3 core and STM32F1xx specific device support is included in the STM32 Standard Peripheral Library. The file that actually does the work is system_stm32f10x.c. Other functions you are performing in BSP_Init() such as flash latency are also dealt with by the CMSIS start-up code. Even if you customise this code, I strongly recommend that you use this method of early environment initialisation.
Another possibility is to use the STM32CubeMX utility to generate configuration code. This appears to be a replacement for the apparently now unavailable STM32 MicroXplorer utility.