Make it possible to get i2c abort reason

Currently we're returning PICO_ERROR_GENERIC for an i2c abort such as
"No ack". Add a new PICO_ERROR_ABORT and use this if
PICO_I2C_RETURN_ABORT_REASON is true.

The abort reason comes from tx_abrt_source
(I2C_IC_TX_ABRT_SOURCE_ABRT_*_BITS) so take the zero count from
PICO_ERROR_ABORT, so the reason can be determined from the return code.

Fixes #1049

src/common/pico_base_headers/include/pico/error.h

@@ -42,7 +42,8 @@ enum pico_error_codes {
     PICO_ERROR_UNSUPPORTED_MODIFICATION = -18,  ///< Write is impossible based on previous writes; e.g. attempted to clear an OTP bit
     PICO_ERROR_LOCK_REQUIRED = -19,             ///< A required lock is not owned
     PICO_ERROR_VERSION_MISMATCH = -20,          ///< A version mismatch occurred (e.g. trying to run PIO version 1 code on RP2040)
-    PICO_ERROR_RESOURCE_IN_USE = -21            ///< The call could not proceed because requires resourcesw were unavailable
+    PICO_ERROR_RESOURCE_IN_USE = -21,           ///< The call could not proceed because requires resourcesw were unavailable
+    PICO_ERROR_ABORT = -22,                     ///< The call could not proceed so was aborted
 };
 
 #endif // !__ASSEMBLER__

src/rp2_common/hardware_i2c/i2c.c

@@ -130,6 +130,15 @@ void i2c_set_slave_mode(i2c_inst_t *i2c, bool slave, uint8_t addr) {
     i2c->hw->enable = 1;
 }
 
+// PICO_CONFIG: PICO_I2C_RETURN_ABORT_REASON, change i2c functions to return the abort reason via a return code less than or equal to PICO_ERROR_ABORT, type=bool, default=0, group=harware_i2c
+#if PICO_I2C_RETURN_ABORT_REASON
+// if (ret <= PICO_ERROR_ABORT) abort_reason = PICO_ERROR_ABORT - ret; // one of I2C_IC_TX_ABRT_SOURCE_ABRT_*_LSB
+#define PICO_I2C_MAKE_ABORT_ERROR(A) (PICO_ERROR_ABORT - __builtin_ctz(A))
+#else
+// By default, for compatibility, return PICO_ERROR_GENERIC if an abort occurs
+#define PICO_I2C_MAKE_ABORT_ERROR(A) PICO_ERROR_GENERIC
+#endif
+
 static int i2c_write_blocking_internal(i2c_inst_t *i2c, uint8_t addr, const uint8_t *src, size_t len, bool nostop,
                                        check_timeout_fn timeout_check, struct timeout_state *ts) {
     invalid_params_if(HARDWARE_I2C, addr >= 0x80); // 7-bit addresses
@@ -225,13 +234,13 @@ static int i2c_write_blocking_internal(i2c_inst_t *i2c, uint8_t addr, const uint
         else if (!abort_reason || abort_reason & I2C_IC_TX_ABRT_SOURCE_ABRT_7B_ADDR_NOACK_BITS) {
             // No reported errors - seems to happen if there is nothing connected to the bus.
             // Address byte not acknowledged
-            rval = PICO_ERROR_GENERIC;
+            rval = PICO_I2C_MAKE_ABORT_ERROR(I2C_IC_TX_ABRT_SOURCE_ABRT_7B_ADDR_NOACK_BITS);
         } else if (abort_reason & I2C_IC_TX_ABRT_SOURCE_ABRT_TXDATA_NOACK_BITS) {
             // Address acknowledged, some data not acknowledged
             rval = byte_ctr;
         } else {
             //panic("Unknown abort from I2C instance @%08x: %08x\n", (uint32_t) i2c->hw, abort_reason);
-            rval = PICO_ERROR_GENERIC;
+            rval = PICO_I2C_MAKE_ABORT_ERROR(abort_reason);
         }
     } else {
         rval = byte_ctr;
@@ -319,10 +328,10 @@ static int i2c_read_blocking_internal(i2c_inst_t *i2c, uint8_t addr, uint8_t *ds
         else if (!abort_reason || abort_reason & I2C_IC_TX_ABRT_SOURCE_ABRT_7B_ADDR_NOACK_BITS) {
             // No reported errors - seems to happen if there is nothing connected to the bus.
             // Address byte not acknowledged
-            rval = PICO_ERROR_GENERIC;
+            rval = PICO_I2C_MAKE_ABORT_ERROR(I2C_IC_TX_ABRT_SOURCE_ABRT_7B_ADDR_NOACK_BITS);
         } else {
 //            panic("Unknown abort from I2C instance @%08x: %08x\n", (uint32_t) i2c->hw, abort_reason);
-            rval = PICO_ERROR_GENERIC;
+            rval = PICO_I2C_MAKE_ABORT_ERROR(abort_reason);
         }
     } else {
         rval = byte_ctr;