tpm_tis: Introduce intermediate layer for TPM access

This splits tpm_tis in a high-level protocol part and a low-level interface
for the actual TPM communication. The low-level interface can then be
implemented by additional drivers to provide access to TPMs using other
mechanisms, for example native I2C or SPI transfers, while still reusing
the same TIS protocol implementation.

Though the ioread/iowrite calls cannot fail, other implementations of this
interface might want to return error codes if their communication fails.

This follows the usual pattern of negative values representing errors and
zero representing success. Positive values are not used (yet).

Errors are passed back to the caller if possible. If the interface of a
function does not allow that, it tries to do the most sensible thing it
can, but this might also mean ignoring the error in this instance.

This commit is based on the initial work by Peter Huewe.
Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.com>
Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

drivers/char/tpm/tpm_tis_core.h

@@ -32,6 +32,57 @@ struct tpm_tis_data {
 	bool irq_tested;
 	wait_queue_head_t int_queue;
 	wait_queue_head_t read_queue;
+	const struct tpm_tis_phy_ops *phy_ops;
 };
 
+struct tpm_tis_phy_ops {
+	int (*read_bytes)(struct tpm_tis_data *data, u32 addr, u16 len,
+			  u8 *result);
+	int (*write_bytes)(struct tpm_tis_data *data, u32 addr, u16 len,
+			   u8 *value);
+	int (*read16)(struct tpm_tis_data *data, u32 addr, u16 *result);
+	int (*read32)(struct tpm_tis_data *data, u32 addr, u32 *result);
+	int (*write32)(struct tpm_tis_data *data, u32 addr, u32 src);
+};
+
+static inline int tpm_tis_read_bytes(struct tpm_tis_data *data, u32 addr,
+				     u16 len, u8 *result)
+{
+	return data->phy_ops->read_bytes(data, addr, len, result);
+}
+
+static inline int tpm_tis_read8(struct tpm_tis_data *data, u32 addr, u8 *result)
+{
+	return data->phy_ops->read_bytes(data, addr, 1, result);
+}
+
+static inline int tpm_tis_read16(struct tpm_tis_data *data, u32 addr,
+				 u16 *result)
+{
+	return data->phy_ops->read16(data, addr, result);
+}
+
+static inline int tpm_tis_read32(struct tpm_tis_data *data, u32 addr,
+				 u32 *result)
+{
+	return data->phy_ops->read32(data, addr, result);
+}
+
+static inline int tpm_tis_write_bytes(struct tpm_tis_data *data, u32 addr,
+				      u16 len, u8 *value)
+{
+	return data->phy_ops->write_bytes(data, addr, len, value);
+}
+
+static inline int tpm_tis_write8(struct tpm_tis_data *data, u32 addr, u8 value)
+{
+	return data->phy_ops->write_bytes(data, addr, 1, &value);
+}
+
+static inline int tpm_tis_write32(struct tpm_tis_data *data, u32 addr,
+				  u32 value)
+{
+	return data->phy_ops->write32(data, addr, value);
+}
+
 #endif