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bluetooth: hci: spi: warn about l2cap MTU values

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`CONFIG_BT_L2CAP_TX_MTU` drives the maximum supported MTU on a Bluetooth
connection, but the SPI backend also imposes its own hidden limits.

Display a warning if a value is chosen that can result in failures to
send. This is done here instead of as a range on `BT_L2CAP_TX_MTU` as
ranges on that symbol are already defined in terms of software features,
which would conflict with this check.

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>
This commit is contained in:
Jordan Yates 2023-05-09 20:57:32 +10:00 • committed by Carles Cufí
commit 72c94d982c
1 changed files with 12 additions and 1 deletions
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13
drivers/bluetooth/hci/spi.c
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@ -58,6 +58,17 @@ LOG_MODULE_REGISTER(bt_driver);
#define DATA_DELAY_US DT_INST_PROP(0, controller_data_delay_us)
/* Single byte header denoting the buffer type */
#define H4_HDR_SIZE 1
/* Maximum L2CAP MTU that can fit in a single packet */
#define MAX_MTU (SPI_MAX_MSG_LEN - H4_HDR_SIZE - BT_L2CAP_HDR_SIZE - BT_HCI_ACL_HDR_SIZE)
#if CONFIG_BT_L2CAP_TX_MTU > MAX_MTU
#warning CONFIG_BT_L2CAP_TX_MTU is too large and can result in packets that cannot \
be transmitted across this HCI link
#endif /* CONFIG_BT_L2CAP_TX_MTU > MAX_MTU */
static uint8_t rxmsg[SPI_MAX_MSG_LEN];
static uint8_t txmsg[SPI_MAX_MSG_LEN];
@ -403,7 +414,7 @@ static int bt_spi_send(struct net_buf *buf)
/* Buffer needs an additional byte for type */
if (buf->len >= SPI_MAX_MSG_LEN) {
LOG_ERR("Message too long");
LOG_ERR("Message too long (%d)", buf->len);
return -EINVAL;
}