CDC epout_buf and epin_buf sizes should be different

[bremenpl]

Operating System

Others

Board

KA-NUCLEO-F411CE

Firmware

src\class\cdc\cdc_device.c

What happened ?

I have described the issue in this post exactly: #1923 (comment)

The problem in a nutshell, is that the 'epout_buf' and 'epin_buf" members of the 'cdcd_interface_t' struct should be allowed to have different sizes, that correspond to the rx_ff_buf and tx_ff_buf sizes consequently.

How to reproduce ?

1. Power up a CDC device example,
2. In the config file, change the 'CFG_TUD_CDC_RX_BUFSIZE value to 1 lower than 'CFG_TUD_CDC_EP_BUFSIZE is set to.
3. Observe how the stack starts to work unstable and the tud_cdc_rx_cb function is not called.

To solve the issue, set 'epout_buf' size to not higher than the rx_ff_buf size. So currently for everything to work as expected, the CFG_TUD_CDC_RX_BUFSIZE has to be >= CFG_TUD_CDC_EP_BUFSIZE. IMO that should not be the case. For example, in my application I wanted to set the CFG_TUD_CDC_RX_BUFSIZE to 0, so I don't use reception at all, as it is not needed.

If I do this:

// CDC FIFO size of TX and RX
#define CFG_TUD_CDC_RX_BUFSIZE   	(0) // <- no RX buffer
#define CFG_TUD_CDC_TX_BUFSIZE   	(128)

// CDC Endpoint transfer buffer size, more is faster
#define CFG_TUD_CDC_EP_BUFSIZE   	(128)

and this:

  uint8_t rx_ff_buf[CFG_TUD_CDC_RX_BUFSIZE];
  uint8_t tx_ff_buf[CFG_TUD_CDC_TX_BUFSIZE];

  OSAL_MUTEX_DEF(rx_ff_mutex);
  OSAL_MUTEX_DEF(tx_ff_mutex);

  // Endpoint Transfer buffer
  CFG_TUSB_MEM_ALIGN uint8_t epout_buf[CFG_TUD_CDC_RX_BUFSIZE]; // <-- replaced the size to the give 0
  CFG_TUSB_MEM_ALIGN uint8_t epin_buf[CFG_TUD_CDC_EP_BUFSIZE];

}cdcd_interface_t;

I can then runy the CDC with only transmission working and nothing crashing when I try to send data from the host to the device/

Debug Log as txt file

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Screenshots

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I have checked existing issues, dicussion and documentation

• I confirm I have checked existing issues, dicussion and documentation.