pios_usb_cdc.c

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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 * for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, see <http://www.gnu.org/licenses/>
 */

/* Project Includes */
#include "pios.h"

#if defined(PIOS_INCLUDE_USB_CDC)

#include "pios_usb.h"
#include "pios_usb_cdc_priv.h"
#include "pios_usb_board_data.h" /* PIOS_BOARD_*_DATA_LENGTH */
#include "pios_usbhook.h"        /* PIOS_USBHOOK_* */

/* Implement COM layer driver API */
static void PIOS_USB_CDC_RegisterTxCallback(uintptr_t usbcdc_id, pios_com_callback tx_out_cb, uintptr_t context);
static void PIOS_USB_CDC_RegisterRxCallback(uintptr_t usbcdc_id, pios_com_callback rx_in_cb, uintptr_t context);
static void PIOS_USB_CDC_TxStart(uintptr_t usbcdc_id, uint16_t tx_bytes_avail);
static void PIOS_USB_CDC_RxStart(uintptr_t usbcdc_id, uint16_t rx_bytes_avail);
static bool PIOS_USB_CDC_Available (uintptr_t usbcdc_id);

const struct pios_com_driver pios_usb_cdc_com_driver = {
        .tx_start    = PIOS_USB_CDC_TxStart,
        .rx_start    = PIOS_USB_CDC_RxStart,
        .bind_tx_cb  = PIOS_USB_CDC_RegisterTxCallback,
        .bind_rx_cb  = PIOS_USB_CDC_RegisterRxCallback,
        .available   = PIOS_USB_CDC_Available,
};

enum pios_usb_cdc_dev_magic {
        PIOS_USB_CDC_DEV_MAGIC = 0xAABBCCDD,
};

struct pios_usb_cdc_dev {
        enum pios_usb_cdc_dev_magic     magic;
        const struct pios_usb_cdc_cfg * cfg;

        uintptr_t lower_id;

        pios_com_callback rx_in_cb;
        uintptr_t rx_in_context;
        pios_com_callback tx_out_cb;
        uintptr_t tx_out_context;

        bool usb_ctrl_if_enabled;
        bool usb_data_if_enabled;

        uint8_t rx_packet_buffer[PIOS_USB_BOARD_CDC_DATA_LENGTH] __attribute__ ((aligned(4)));
        volatile bool rx_active;

        /*
         * NOTE: This is -1 as somewhat of a hack.  It ensures that we always send packets
         * that are strictly < maxPacketSize for this interface which means we never have
         * to bother with zero length packets (ZLP).
         */
        uint8_t tx_packet_buffer[PIOS_USB_BOARD_CDC_DATA_LENGTH - 1] __attribute__ ((aligned(4)));
        volatile bool tx_active;

        uint8_t ctrl_tx_packet_buffer[PIOS_USB_BOARD_CDC_MGMT_LENGTH] __attribute__ ((aligned(4)));

        uint32_t rx_dropped;
        uint32_t rx_oversize;

        /*
         * Used to hold the current state of the simulated UART.  Changes to this 
         * variable may trigger new USB CDC Notification packets to be sent to the host.
         */
        volatile uint16_t prev_uart_state;
};

static bool PIOS_USB_CDC_validate(struct pios_usb_cdc_dev * usb_cdc_dev)
{
        return (usb_cdc_dev && (usb_cdc_dev->magic == PIOS_USB_CDC_DEV_MAGIC));
}

static struct pios_usb_cdc_dev * PIOS_USB_CDC_alloc(void)
{
        struct pios_usb_cdc_dev * usb_cdc_dev;

        usb_cdc_dev = (struct pios_usb_cdc_dev *)PIOS_malloc(sizeof(*usb_cdc_dev));
        if (!usb_cdc_dev) return(NULL);

        memset(usb_cdc_dev, 0, sizeof(*usb_cdc_dev));
        usb_cdc_dev->magic = PIOS_USB_CDC_DEV_MAGIC;
        return(usb_cdc_dev);
}

/* Implement USB_IFOPS for CDC Control Interface */
static void PIOS_USB_CDC_CTRL_IF_Init(uintptr_t usb_cdc_id);
static void PIOS_USB_CDC_CTRL_IF_DeInit(uintptr_t usb_cdc_id);
static bool PIOS_USB_CDC_CTRL_IF_Setup(uintptr_t usb_cdc_id, struct usb_setup_request *req);
static void PIOS_USB_CDC_CTRL_IF_CtrlDataOut(uintptr_t usb_cdc_id, const struct usb_setup_request *req);

static struct pios_usb_ifops usb_cdc_ctrl_ifops = {
        .init          = PIOS_USB_CDC_CTRL_IF_Init,
        .deinit        = PIOS_USB_CDC_CTRL_IF_DeInit,
        .setup         = PIOS_USB_CDC_CTRL_IF_Setup,
        .ctrl_data_out = PIOS_USB_CDC_CTRL_IF_CtrlDataOut,
};

/* Implement USB_IFOPS for CDC Data Interface */
static void PIOS_USB_CDC_DATA_IF_Init(uintptr_t usb_cdc_id);
static void PIOS_USB_CDC_DATA_IF_DeInit(uintptr_t usb_cdc_id);
static bool PIOS_USB_CDC_DATA_IF_Setup(uintptr_t usb_cdc_id, struct usb_setup_request *req);
static void PIOS_USB_CDC_DATA_IF_CtrlDataOut(uintptr_t usb_cdc_id, const struct usb_setup_request *req);

static struct pios_usb_ifops usb_cdc_data_ifops = {
        .init          = PIOS_USB_CDC_DATA_IF_Init,
        .deinit        = PIOS_USB_CDC_DATA_IF_DeInit,
        .setup         = PIOS_USB_CDC_DATA_IF_Setup,
        .ctrl_data_out = PIOS_USB_CDC_DATA_IF_CtrlDataOut,
};

static uintptr_t pios_usb_cdc_id;

int32_t PIOS_USB_CDC_Init(uintptr_t * usbcdc_id, const struct pios_usb_cdc_cfg * cfg, uintptr_t lower_id)
{
        PIOS_Assert(usbcdc_id);
        PIOS_Assert(cfg);

        struct pios_usb_cdc_dev * usb_cdc_dev;

        usb_cdc_dev = (struct pios_usb_cdc_dev *) PIOS_USB_CDC_alloc();
        if (!usb_cdc_dev) goto out_fail;

        /* Bind the configuration to the device instance */
        usb_cdc_dev->cfg = cfg;
        usb_cdc_dev->lower_id = lower_id;

        pios_usb_cdc_id = (uintptr_t) usb_cdc_dev;

        /* Rx and Tx are not active yet */
        usb_cdc_dev->rx_active = false;
        usb_cdc_dev->tx_active = false;

        /* Clear stats */
        usb_cdc_dev->rx_dropped = 0;
        usb_cdc_dev->rx_oversize = 0;

        /* Initialize the uart state */
        usb_cdc_dev->prev_uart_state = 0;

        /* Register class specific interface callbacks with the USBHOOK layer */
        usb_cdc_dev->usb_ctrl_if_enabled = false;
        PIOS_USBHOOK_RegisterIfOps(cfg->ctrl_if, &usb_cdc_ctrl_ifops, (uintptr_t) usb_cdc_dev);

        /* Register class specific interface callbacks with the USBHOOK layer */
        usb_cdc_dev->usb_data_if_enabled = false;
        PIOS_USBHOOK_RegisterIfOps(cfg->data_if, &usb_cdc_data_ifops, (uintptr_t) usb_cdc_dev);

        *usbcdc_id = (uintptr_t) usb_cdc_dev;

        return 0;

out_fail:
        return -1;
}

static bool PIOS_USB_CDC_SendData(struct pios_usb_cdc_dev * usb_cdc_dev)
{
        uint16_t bytes_to_tx;

        if (!usb_cdc_dev->tx_out_cb) {
                return false;
        }

        bool need_yield = false;
        bytes_to_tx = (usb_cdc_dev->tx_out_cb)(usb_cdc_dev->tx_out_context,
                                               usb_cdc_dev->tx_packet_buffer,
                                               sizeof(usb_cdc_dev->tx_packet_buffer),
                                               NULL,
                                               &need_yield);
        if (bytes_to_tx == 0) {
                usb_cdc_dev->tx_active = false;

                return false;
        }

        /* 
         * Mark this endpoint as being tx active _before_ actually transmitting
         * to make sure we don't race with the Tx completion interrupt
         */
        usb_cdc_dev->tx_active = true;

        PIOS_USBHOOK_EndpointTx(usb_cdc_dev->cfg->data_tx_ep,
                                usb_cdc_dev->tx_packet_buffer,
                                bytes_to_tx);

        return true;
}

static void PIOS_USB_CDC_RxStart(uintptr_t usbcdc_id, uint16_t rx_bytes_avail) {
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)usbcdc_id;

        bool valid = PIOS_USB_CDC_validate(usb_cdc_dev);
        PIOS_Assert(valid);

        /* Make sure this USB interface has been initialized */
        if (!usb_cdc_dev->usb_data_if_enabled) {
                return;
        }

        if (!PIOS_USB_CheckAvailable(usb_cdc_dev->lower_id)) {
                return;
        }

        // If endpoint was stalled and there is now space make it valid
        if (!usb_cdc_dev->rx_active && (rx_bytes_avail >= PIOS_USB_BOARD_CDC_DATA_LENGTH)) {
                PIOS_USBHOOK_EndpointRx(usb_cdc_dev->cfg->data_rx_ep,
                                        usb_cdc_dev->rx_packet_buffer,
                                        sizeof(usb_cdc_dev->rx_packet_buffer));
                usb_cdc_dev->rx_active = true;
        }
}

static void PIOS_USB_CDC_TxStart(uintptr_t usbcdc_id, uint16_t tx_bytes_avail)
{
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)usbcdc_id;

        bool valid = PIOS_USB_CDC_validate(usb_cdc_dev);
        PIOS_Assert(valid);

        /* Make sure this USB interface has been initialized */
        if (!usb_cdc_dev->usb_data_if_enabled) {
                return;
        }

        if (!PIOS_USB_CheckAvailable(usb_cdc_dev->lower_id)) {
                return;
        }

        if (!usb_cdc_dev->tx_active) {
                /* Transmitter is not currently active, send a report */
                PIOS_USB_CDC_SendData(usb_cdc_dev);
        }
}

static void PIOS_USB_CDC_RegisterRxCallback(uintptr_t usbcdc_id, pios_com_callback rx_in_cb, uintptr_t context)
{
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)usbcdc_id;

        bool valid = PIOS_USB_CDC_validate(usb_cdc_dev);
        PIOS_Assert(valid);

        /* 
         * Order is important in these assignments since ISR uses _cb
         * field to determine if it's ok to dereference _cb and _context
         */
        usb_cdc_dev->rx_in_context = context;
        usb_cdc_dev->rx_in_cb = rx_in_cb;
}

static void PIOS_USB_CDC_RegisterTxCallback(uintptr_t usbcdc_id, pios_com_callback tx_out_cb, uintptr_t context)
{
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)usbcdc_id;

        bool valid = PIOS_USB_CDC_validate(usb_cdc_dev);
        PIOS_Assert(valid);

        /* 
         * Order is important in these assignments since ISR uses _cb
         * field to determine if it's ok to dereference _cb and _context
         */
        usb_cdc_dev->tx_out_context = context;
        usb_cdc_dev->tx_out_cb = tx_out_cb;
}

static bool PIOS_USB_CDC_CTRL_EP_IN_Callback(uintptr_t usb_cdc_id, uint8_t epnum, uint16_t len);

static void PIOS_USB_CDC_CTRL_IF_Init(uintptr_t usb_cdc_id)
{
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)usb_cdc_id;

        if (!PIOS_USB_CDC_validate(usb_cdc_dev)) {
                return;
        }

        /* Register endpoint specific callbacks with the USBHOOK layer */
        PIOS_USBHOOK_RegisterEpInCallback(usb_cdc_dev->cfg->ctrl_tx_ep,
                                          sizeof(usb_cdc_dev->ctrl_tx_packet_buffer),
                                          PIOS_USB_CDC_CTRL_EP_IN_Callback,
                                          (uintptr_t) usb_cdc_dev);
        usb_cdc_dev->usb_ctrl_if_enabled = true;
}

static void PIOS_USB_CDC_CTRL_IF_DeInit(uintptr_t usb_cdc_id)
{
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)usb_cdc_id;

        if (!PIOS_USB_CDC_validate(usb_cdc_dev)) {
                return;
        }

        /* reset state of the usb hid device structure */
        usb_cdc_dev->usb_ctrl_if_enabled = false;
}

static uint8_t cdc_altset;
static struct usb_cdc_line_coding line_coding = {
        .dwDTERate   = htousbl(57600),
        .bCharFormat = USB_CDC_LINE_CODING_STOP_1,
        .bParityType = USB_CDC_LINE_CODING_PARITY_NONE,
        .bDataBits   = 8,
};

static uint16_t control_line_state;

static bool PIOS_USB_CDC_CTRL_IF_Setup(uintptr_t usb_cdc_id, struct usb_setup_request *req)
{
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)usb_cdc_id;

        if (!PIOS_USB_CDC_validate(usb_cdc_dev)) {
                return false;
        }

        /* Make sure this is a request for an interface we know about */
        uint8_t ifnum = req->wIndex & 0xFF;
        if (ifnum != usb_cdc_dev->cfg->ctrl_if) {
                return (false);
        }

        switch (req->bmRequestType & (USB_REQ_TYPE_MASK | USB_REQ_RECIPIENT_MASK)) {
        case (USB_REQ_TYPE_STANDARD | USB_REQ_RECIPIENT_INTERFACE):
                switch (req->bRequest) {
                case USB_REQ_GET_INTERFACE:
                        PIOS_USBHOOK_CtrlTx(&cdc_altset, 1);
                        break;
                case USB_REQ_SET_INTERFACE:
                        cdc_altset = (uint8_t)(req->wValue);
                        break;
                default:
                        /* Unhandled standard request */
                        return false;
                        break;
                }
                break;
        case (USB_REQ_TYPE_CLASS    | USB_REQ_RECIPIENT_INTERFACE):
                switch (req->bRequest) {
                case USB_CDC_REQ_SET_LINE_CODING:
                        PIOS_USBHOOK_CtrlRx((uint8_t *)&line_coding, sizeof(line_coding));
                        break;
                case USB_CDC_REQ_GET_LINE_CODING:
                        PIOS_USBHOOK_CtrlTx((uint8_t *)&line_coding, sizeof(line_coding));
                        break;
                case USB_CDC_REQ_SET_CONTROL_LINE_STATE:
                        control_line_state = req->wValue;
                        break;
                default:
                        /* Unhandled class request */
                        return false;
                        break;
                }
                break;
        default:
                /* Unhandled request */
                return false;
        }

        return true;
}

static bool PIOS_USB_CDC_Available (uintptr_t usbcdc_id)
{
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)usbcdc_id;

        bool valid = PIOS_USB_CDC_validate(usb_cdc_dev);
        PIOS_Assert(valid);

        return PIOS_USB_CheckAvailable(usb_cdc_dev->lower_id);
}

static void PIOS_USB_CDC_CTRL_IF_CtrlDataOut(uintptr_t usb_cdc_id, const struct usb_setup_request *req)
{
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)usb_cdc_id;

        if (!PIOS_USB_CDC_validate(usb_cdc_dev)) {
                return;
        }

        /* Make sure this is a request for an interface we know about */
        uint8_t ifnum = req->wIndex & 0xFF;
        if (ifnum != usb_cdc_dev->cfg->ctrl_if) {
                return;
        }

        switch (req->bmRequestType & (USB_REQ_TYPE_MASK | USB_REQ_RECIPIENT_MASK)) {
        case (USB_REQ_TYPE_STANDARD | USB_REQ_RECIPIENT_INTERFACE):
                switch (req->bRequest) {
                default:
                        /* Unhandled standard request */
                        return;
                        break;
                }
                break;
        case (USB_REQ_TYPE_CLASS    | USB_REQ_RECIPIENT_INTERFACE):
                switch (req->bRequest) {
                case USB_CDC_REQ_SET_LINE_CODING:
                        /*
                         * If we cared to, this is where we would apply the new line coding
                         * that is now stored in the line_coding struct.  This could be used
                         * to notify the upper COM layer that the baud rate has changed.  This
                         * may be useful in the case of a COM USB bridge where we would
                         * auto-adjust the USART baud rate based on the line coding set here.
                         */
                        break;
                default:
                        /* Unhandled class request */
                        return;
                        break;
                }
                break;
        default:
                /* Unhandled request */
                return;
        }

        return;
}

static struct usb_cdc_serial_state_report uart_state = {
        .bmRequestType = 0xA1,
        .bNotification = USB_CDC_NOTIFICATION_SERIAL_STATE,
        .wValue        = 0,
        .wIndex        = htousbs(1),
        .wLength       = htousbs(2),
        .bmUartState   = htousbs(2 /* DSR */ | 1 /* DCD */),
};
        
static bool PIOS_USB_CDC_CTRL_EP_IN_Callback(uintptr_t usb_cdc_id, uint8_t epnum, uint16_t len)
{
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)pios_usb_cdc_id;

        bool valid = PIOS_USB_CDC_validate(usb_cdc_dev);
        PIOS_Assert(valid);

        PIOS_USBHOOK_EndpointTx(usb_cdc_dev->cfg->ctrl_tx_ep,
                        (uint8_t *)&uart_state,
                        sizeof(uart_state));

        return true;
}

static bool PIOS_USB_CDC_DATA_EP_IN_Callback(uintptr_t usb_cdc_id, uint8_t epnum, uint16_t len);
static bool PIOS_USB_CDC_DATA_EP_OUT_Callback(uintptr_t usb_cdc_id, uint8_t epnum, uint16_t len);

static void PIOS_USB_CDC_DATA_IF_Init(uintptr_t usb_cdc_id)
{
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)usb_cdc_id;

        if (!PIOS_USB_CDC_validate(usb_cdc_dev)) {
                return;
        }

        /* Register endpoint specific callbacks with the USBHOOK layer */
        PIOS_USBHOOK_RegisterEpInCallback(usb_cdc_dev->cfg->data_tx_ep,
                                          sizeof(usb_cdc_dev->tx_packet_buffer),
                                          PIOS_USB_CDC_DATA_EP_IN_Callback,
                                          (uintptr_t) usb_cdc_dev);
        PIOS_USBHOOK_RegisterEpOutCallback(usb_cdc_dev->cfg->data_rx_ep,
                                           sizeof(usb_cdc_dev->rx_packet_buffer),
                                           PIOS_USB_CDC_DATA_EP_OUT_Callback,
                                           (uintptr_t) usb_cdc_dev);
        usb_cdc_dev->usb_data_if_enabled = true;
}

static void PIOS_USB_CDC_DATA_IF_DeInit(uintptr_t usb_cdc_id)
{
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)usb_cdc_id;

        if (!PIOS_USB_CDC_validate(usb_cdc_dev)) {
                return;
        }

        /* reset state of the usb hid device structure */
        usb_cdc_dev->rx_active = false;
        usb_cdc_dev->rx_dropped = 0;
        usb_cdc_dev->rx_oversize = 0;
        usb_cdc_dev->tx_active = false;
        usb_cdc_dev->usb_data_if_enabled = false;

        /* DeRegister endpoint specific callbacks with the USBHOOK layer */
        PIOS_USBHOOK_DeRegisterEpInCallback(usb_cdc_dev->cfg->data_tx_ep);
        PIOS_USBHOOK_DeRegisterEpOutCallback(usb_cdc_dev->cfg->data_rx_ep);
}

static bool PIOS_USB_CDC_DATA_IF_Setup(uintptr_t usb_cdc_id, struct usb_setup_request *req)
{
        /* There are no valid EP0 transactions for CDC DATA interfaces */
        PIOS_Assert(0);

        return false;
}

static void PIOS_USB_CDC_DATA_IF_CtrlDataOut(uintptr_t usb_cdc_id, const struct usb_setup_request *req)
{
        /* CDC DATA interfaces don't have any OUT data stages on the control endpoint */
        PIOS_Assert(0);
}

static bool PIOS_USB_CDC_DATA_EP_IN_Callback(uintptr_t usb_cdc_id, uint8_t epnum, uint16_t len)
{
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)pios_usb_cdc_id;

        bool valid = PIOS_USB_CDC_validate(usb_cdc_dev);
        PIOS_Assert(valid);

        bool rc = PIOS_USB_CDC_SendData(usb_cdc_dev);

        return rc;
}

static bool PIOS_USB_CDC_DATA_EP_OUT_Callback(uintptr_t usb_cdc_id, uint8_t epnum, uint16_t len)
{
        struct pios_usb_cdc_dev * usb_cdc_dev = (struct pios_usb_cdc_dev *)pios_usb_cdc_id;

        if (!PIOS_USB_CDC_validate(usb_cdc_dev)) {
                return false;
        }

        if (len > sizeof(usb_cdc_dev->rx_packet_buffer)) {
                len = sizeof(usb_cdc_dev->rx_packet_buffer);
        }

        if (!usb_cdc_dev->rx_in_cb) {
                /* No Rx call back registered, disable the receiver */
                usb_cdc_dev->rx_active = false;
                return false;
        }

        uint16_t headroom;
        bool need_yield = false;
        uint16_t bytes_rxed;
        bytes_rxed = (usb_cdc_dev->rx_in_cb)(usb_cdc_dev->rx_in_context,
                                        usb_cdc_dev->rx_packet_buffer,
                                        len,
                                        &headroom,
                                        &need_yield);

        if (bytes_rxed < len) {
                /* Lost bytes on rx */
                usb_cdc_dev->rx_dropped += (len - bytes_rxed);
        }

        bool rc;
        if (headroom >= sizeof(usb_cdc_dev->rx_packet_buffer)) {
                /* We have room for a maximum length message */
                PIOS_USBHOOK_EndpointRx(usb_cdc_dev->cfg->data_rx_ep,
                                        usb_cdc_dev->rx_packet_buffer,
                                        sizeof(usb_cdc_dev->rx_packet_buffer));
                rc = true;
        } else {
                /* Not enough room left for a message, apply backpressure */
                usb_cdc_dev->rx_active = false;
                rc = false;
        }

        return rc;
}

#endif  /* PIOS_INCLUDE_USB_CDC */