Re: [PATCH 3/3] i2c: Add Intel USBIO I2C driver

Sakari Ailus
2025-08-11T07:16:57Z

Hi Hans, Israel,

My comments on newlines and parentheses apply to this one, too; I'm not
making new ones in similar locations on that subject anymore for this
patch.

On Sat, Aug 09, 2025 at 12:23:26PM +0200, Hans de Goede wrote:
> From: Israel Cepeda <israel.a.cepeda.lopez@intel.com>
>
> Add a a driver for the I2C auxbus child device of the Intel USBIO USB
> IO-expander used by the MIPI cameras on various new (Meteor Lake and
> later) Intel laptops.
>
> Co-developed-by: Hans de Goede <hansg@kernel.org>
> Signed-off-by: Hans de Goede <hansg@kernel.org>
> Signed-off-by: Israel Cepeda <israel.a.cepeda.lopez@intel.com>
> ---
> MAINTAINERS | 1 +
> drivers/i2c/busses/Kconfig | 11 ++
> drivers/i2c/busses/Makefile | 1 +
> drivers/i2c/busses/i2c-usbio.c | 344 +++++++++++++++++++++++++++++++++
> 4 files changed, 357 insertions(+)
> create mode 100644 drivers/i2c/busses/i2c-usbio.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 81db1457e9d1..9e8875e3dabf 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12523,6 +12523,7 @@ M: Israel Cepeda <israel.a.cepeda.lopez@intel.com>
> M: Hans de Goede <hansg@kernel.org>
> S: Maintained
> F: drivers/gpio/gpio-usbio.c
> +F: drivers/i2c/busses/i2c-usbio.c
> F: drivers/usb/misc/usbio.c
> F: include/linux/usb/usbio.h
>
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index c8d115b58e44..bf6a624f5ff6 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -1358,6 +1358,17 @@ config I2C_LJCA
> This driver can also be built as a module. If so, the module
> will be called i2c-ljca.
>
> +config I2C_USBIO
> + tristate "Intel USBIO I2C Adapter support"
> + depends on USB_USBIO
> + default USB_USBIO
> + help
> + Select this option to enable I2C driver for the INTEL
> + USBIO driver stack.
> +
> + This driver can also be built as a module. If so, the module
> + will be called i2c_usbio.
> +
> config I2C_CP2615
> tristate "Silicon Labs CP2615 USB sound card and I2C adapter"
> depends on USB
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index 04db855fdfd6..401a79c9767e 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -135,6 +135,7 @@ obj-$(CONFIG_I2C_GXP) += i2c-gxp.o
> obj-$(CONFIG_I2C_DIOLAN_U2C) += i2c-diolan-u2c.o
> obj-$(CONFIG_I2C_DLN2) += i2c-dln2.o
> obj-$(CONFIG_I2C_LJCA) += i2c-ljca.o
> +obj-$(CONFIG_I2C_USBIO) += i2c-usbio.o
> obj-$(CONFIG_I2C_CP2615) += i2c-cp2615.o
> obj-$(CONFIG_I2C_PARPORT) += i2c-parport.o
> obj-$(CONFIG_I2C_PCI1XXXX) += i2c-mchp-pci1xxxx.o
> diff --git a/drivers/i2c/busses/i2c-usbio.c b/drivers/i2c/busses/i2c-usbio.c
> new file mode 100644
> index 000000000000..82c4769852f8
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-usbio.c
> @@ -0,0 +1,344 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2025 Intel Corporation.
> + * Copyright (c) 2025 Red Hat, Inc.
> + */
> +
> +#include <linux/auxiliary_bus.h>
> +#include <linux/dev_printk.h>
> +#include <linux/device.h>
> +#include <linux/i2c.h>
> +#include <linux/types.h>
> +#include <linux/usb/usbio.h>
> +
> +#define I2C_RW_OVERHEAD (sizeof(struct usbio_bulk_packet) + sizeof(struct usbio_i2c_rw))
> +
> +struct usbio_i2c {
> + u32 speed;

You could declare this with the smaller fields for better struct packing.

> + struct i2c_adapter adap;
> + struct auxiliary_device *adev;
> + struct usbio_i2c_rw *rwbuf;
> + bool init_supports_ack_flag;
> + u16 txbuf_len;
> + u16 rxbuf_len;
> +};
> +
> +static const struct acpi_device_id usbio_i2c_acpi_hids[] = {
> + { "INTC1008" }, /* MTL */
> + { "INTC10B3" }, /* ARL */
> + { "INTC10B6" }, /* LNL */
> + { "INTC10E3" }, /* PTL */
> + { }
> +};
> +
> +static const u32 usbio_i2c_speeds[] = {
> + I2C_MAX_STANDARD_MODE_FREQ,
> + I2C_MAX_FAST_MODE_FREQ,
> + I2C_MAX_FAST_MODE_PLUS_FREQ,
> + I2C_MAX_HIGH_SPEED_MODE_FREQ
> +};
> +
> +static void usbio_i2c_uninit(struct i2c_adapter *adap, struct i2c_msg *msg)
> +{
> + struct usbio_i2c *i2c = i2c_get_adapdata(adap);
> + struct usbio_i2c_uninit ubuf;
> +
> + ubuf.busid = i2c->adev->id;
> + ubuf.config = msg->addr;

You can initialise this in declaration.

> +
> + usbio_bulk_msg(i2c->adev, USBIO_PKTTYPE_I2C, USBIO_I2CCMD_UNINIT, true,
> + &ubuf, sizeof(ubuf), NULL, 0);
> +}
> +
> +static int usbio_i2c_init(struct i2c_adapter *adap, struct i2c_msg *msg)
> +{
> + struct usbio_i2c *i2c = i2c_get_adapdata(adap);
> + struct usbio_i2c_init ibuf;
> + void *reply_buf;
> + u16 reply_len;
> + int ret;
> +
> + ibuf.busid = i2c->adev->id;
> + ibuf.config = msg->addr;
> + ibuf.speed = i2c->speed;

Ditto.

> +
> + if (i2c->init_supports_ack_flag) {
> + reply_buf = &ibuf;
> + reply_len = sizeof(ibuf);
> + } else {
> + reply_buf = NULL;
> + reply_len = 0;
> + }
> + ret = usbio_bulk_msg(i2c->adev, USBIO_PKTTYPE_I2C, USBIO_I2CCMD_INIT, true,
> + &ibuf, sizeof(ibuf), reply_buf, reply_len);
> + if (ret != sizeof(ibuf))
> + return (ret < 0) ? ret : -EIO;
> +
> + return 0;
> +}
> +
> +static int usbio_i2c_read(struct i2c_adapter *adap, struct i2c_msg *msg)
> +{
> + struct usbio_i2c *i2c = i2c_get_adapdata(adap);
> + u16 rxchunk = i2c->rxbuf_len - I2C_RW_OVERHEAD;
> + struct usbio_i2c_rw *rbuf = i2c->rwbuf;
> + int ret;
> +
> + rbuf->busid = i2c->adev->id;
> + rbuf->config = msg->addr;
> + rbuf->size = msg->len;
> +
> + if (msg->len > rxchunk) {
> + /* Need to split the input buffer */
> + u16 len = 0;
> +
> + do {
> + if (msg->len - len < rxchunk)
> + rxchunk = msg->len - len;
> +
> + ret = usbio_bulk_msg(i2c->adev, USBIO_PKTTYPE_I2C,
> + USBIO_I2CCMD_READ, true,
> + rbuf, len == 0 ? sizeof(*rbuf) : 0,
> + rbuf, sizeof(*rbuf) + rxchunk);
> + if (ret < 0)
> + return ret;
> +
> + memcpy(&msg->buf[len], rbuf->data, rxchunk);
> + len += rxchunk;
> + } while (msg->len > len);
> +
> + goto out_log;
> + }
> +
> + ret = usbio_bulk_msg(i2c->adev, USBIO_PKTTYPE_I2C, USBIO_I2CCMD_READ, true,
> + rbuf, sizeof(*rbuf), rbuf, sizeof(*rbuf) + msg->len);
> + if (ret != sizeof(*rbuf) + msg->len)
> + return (ret < 0) ? ret : -EIO;
> +
> + memcpy(msg->buf, rbuf->data, msg->len);

An extra newline here?

> +out_log:
> + dev_dbg(adap->dev.parent, "RD[%d]:%*phN\n", msg->len, msg->len, msg->buf);
> + return 0;
> +}
> +
> +static int usbio_i2c_write(struct i2c_adapter *adap, struct i2c_msg *msg)
> +{
> + struct usbio_i2c *i2c = i2c_get_adapdata(adap);
> + u16 txchunk = i2c->txbuf_len - I2C_RW_OVERHEAD;
> + struct usbio_i2c_rw *wbuf = i2c->rwbuf;
> + int ret;
> +
> + dev_dbg(adap->dev.parent, "WR[%d]:%*phN\n", msg->len, msg->len, msg->buf);
> +
> + if (msg->len > txchunk) {
> + /* Need to split the output buffer */
> + u16 len = 0;
> +
> + do {
> + wbuf->busid = i2c->adev->id;
> + wbuf->config = msg->addr;
> + wbuf->size = msg->len;
> +
> + memcpy(wbuf->data, &msg->buf[len], txchunk);
> + len += txchunk;
> +
> + ret = usbio_bulk_msg(i2c->adev, USBIO_PKTTYPE_I2C,
> + USBIO_I2CCMD_WRITE, msg->len == len,
> + wbuf, sizeof(*wbuf) + txchunk,
> + wbuf, sizeof(*wbuf));
> + if (ret < 0)
> + return ret;
> +
> + if (msg->len - len < txchunk)
> + txchunk = msg->len - len;
> + } while (msg->len > len);
> +
> + return 0;
> + }
> +
> + wbuf->busid = i2c->adev->id;
> + wbuf->config = msg->addr;
> + wbuf->size = msg->len;
> + memcpy(wbuf->data, msg->buf, msg->len);
> +
> + ret = usbio_bulk_msg(i2c->adev, USBIO_PKTTYPE_I2C, USBIO_I2CCMD_WRITE, true,
> + wbuf, sizeof(*wbuf) + msg->len, wbuf, sizeof(*wbuf));
> + if (ret != sizeof(*wbuf) || wbuf->size != msg->len)
> + return (ret < 0) ? ret : -EIO;
> +
> + return 0;
> +}
> +
> +static int usbio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
> +{
> + struct usbio_i2c *i2c = i2c_get_adapdata(adap);
> + int ret;
> +
> + usbio_acquire(i2c->adev);
> +
> + ret = usbio_i2c_init(adap, msgs);
> + if (ret)
> + goto out_release;
> +
> + for (int i = 0; i < num; ret = ++i) {
> + if (msgs[i].flags & I2C_M_RD)
> + ret = usbio_i2c_read(adap, &msgs[i]);
> + else
> + ret = usbio_i2c_write(adap, &msgs[i]);
> +
> + if (ret)
> + break;
> + }
> +
> + usbio_i2c_uninit(adap, msgs);
> +
> +out_release:
> + usbio_release(i2c->adev);
> + return ret;
> +}
> +
> +static u32 usbio_i2c_func(struct i2c_adapter *adap)
> +{
> + return I2C_FUNC_I2C | I2C_FUNC_10BIT_ADDR | I2C_FUNC_SMBUS_EMUL;
> +}
> +
> +static const struct i2c_adapter_quirks usbio_i2c_quirks = {
> + .flags = I2C_AQ_NO_REP_START,
> + .max_read_len = SZ_4K,
> + .max_write_len = SZ_4K,
> +};
> +
> +/* Use smaller max_*_len settings for chips which do not support split bulk transfers */
> +static const struct i2c_adapter_quirks usbio_i2c_no_split_transfers_quirks = {
> + .flags = I2C_AQ_NO_REP_START,
> + .max_read_len = 63 - I2C_RW_OVERHEAD,
> + .max_write_len = 63 - I2C_RW_OVERHEAD,
> +};
> +
> +static const struct i2c_algorithm usbio_i2c_algo = {
> + .master_xfer = usbio_i2c_xfer,
> + .functionality = usbio_i2c_func,
> +};
> +
> +static int usbio_i2c_probe(struct auxiliary_device *adev,
> + const struct auxiliary_device_id *adev_id)
> +{
> + struct usbio_i2c_bus_desc *i2c_desc;
> + struct device *dev = &adev->dev;
> + u8 dummy_read_buf;
> + struct i2c_msg dummy_read = {
> + .addr = 0x08,
> + .flags = I2C_M_RD,
> + .len = 1,
> + .buf = &dummy_read_buf,
> + };
> + struct usbio_i2c *i2c;
> + u32 max_speed;
> + int ret;
> +
> + i2c_desc = dev_get_platdata(dev);
> + if (!i2c_desc)
> + return -EINVAL;
> +
> + /* Some USBIO chips have caps set to 0, but all chips can do 400KHz */
> + if (!i2c_desc->caps)
> + max_speed = I2C_MAX_FAST_MODE_FREQ;
> + else
> + max_speed = usbio_i2c_speeds[i2c_desc->caps & USBIO_I2C_BUS_MODE_CAP_MASK];
> +
> + i2c = devm_kzalloc(dev, sizeof(*i2c), GFP_KERNEL);
> + if (!i2c)
> + return -ENOMEM;

Same comment on devm memory allocation than on the GPIO driver: I think you
need to use the release callback of struct device here.

> +
> + i2c->adev = adev;
> +
> + usbio_acpi_bind(i2c->adev, usbio_i2c_acpi_hids);
> + usbio_get_txrxbuf_len(i2c->adev, &i2c->txbuf_len, &i2c->rxbuf_len);
> +
> + i2c->rwbuf = devm_kzalloc(dev, max(i2c->txbuf_len, i2c->rxbuf_len), GFP_KERNEL);
> + if (!i2c->rwbuf)
> + return -ENOMEM;

Ditto.

> +
> + i2c->speed = i2c_acpi_find_bus_speed(dev);
> + if (!i2c->speed)
> + i2c->speed = I2C_MAX_STANDARD_MODE_FREQ;
> + else if (i2c->speed > max_speed) {
> + dev_warn(dev, "Invalid speed %u adjusting to bus max %u\n",
> + i2c->speed, max_speed);
> + i2c->speed = max_speed;
> + }
> +
> + i2c->adap.owner = THIS_MODULE;
> + i2c->adap.class = I2C_CLASS_HWMON;
> + i2c->adap.dev.parent = dev;
> + i2c->adap.algo = &usbio_i2c_algo;
> + i2c->adap.quirks = &usbio_i2c_quirks;
> +
> + snprintf(i2c->adap.name, sizeof(i2c->adap.name), "%s.%d",
> + USBIO_I2C_CLIENT, i2c->adev->id);
> +
> + device_set_node(&i2c->adap.dev, dev_fwnode(&adev->dev));
> +
> + auxiliary_set_drvdata(adev, i2c);
> + i2c_set_adapdata(&i2c->adap, i2c);
> +
> + /*
> + * Test if USBIO_I2CCMD_INIT commands with the USBIO_PKTFLAG_ACK flag
> + * are supported.
> + */
> + usbio_acquire(i2c->adev);
> + i2c->init_supports_ack_flag = true;
> + ret = usbio_i2c_init(&i2c->adap, &dummy_read);
> + if (ret) {
> + if (ret != -EPIPE) {
> + usbio_release(i2c->adev);
> + return ret; /* Unexpected error */
> + }
> +
> + dev_info(dev, "i2c-init command does not support ack flag\n");
> + i2c->init_supports_ack_flag = false;
> + /* Chips with this quirk also do not support split bulk transfers */
> + i2c->adap.quirks = &usbio_i2c_no_split_transfers_quirks;
> + } else {
> + /* Continue dummy read to not confuse the USBIO chip */
> + usbio_i2c_read(&i2c->adap, &dummy_read);
> + }
> + usbio_i2c_uninit(&i2c->adap, &dummy_read);
> + usbio_release(i2c->adev);
> +
> + ret = i2c_add_adapter(&i2c->adap);
> + if (ret)
> + return ret;
> +
> + if (has_acpi_companion(&i2c->adap.dev))
> + acpi_dev_clear_dependencies(ACPI_COMPANION(&i2c->adap.dev));
> +
> + return 0;
> +}
> +
> +static void usbio_i2c_remove(struct auxiliary_device *adev)
> +{
> + struct usbio_i2c *i2c = auxiliary_get_drvdata(adev);
> +
> + i2c_del_adapter(&i2c->adap);
> +}
> +
> +static const struct auxiliary_device_id usbio_i2c_id_table[] = {
> + { "usbio.usbio-i2c" },
> + { }
> +};
> +MODULE_DEVICE_TABLE(auxiliary, usbio_i2c_id_table);
> +
> +static struct auxiliary_driver usbio_i2c_driver = {
> + .name = USBIO_I2C_CLIENT,
> + .probe = usbio_i2c_probe,
> + .remove = usbio_i2c_remove,
> + .id_table = usbio_i2c_id_table
> +};
> +module_auxiliary_driver(usbio_i2c_driver);
> +
> +MODULE_DESCRIPTION("Intel USBIO I2C driver");
> +MODULE_AUTHOR("Israel Cepeda <israel.a.cepeda.lopez@intel.com>");
> +MODULE_AUTHOR("Hans de Goede <hansg@kernel.org>");
> +MODULE_LICENSE("GPL");
> +MODULE_IMPORT_NS("USBIO");

--
Kind regards,

Sakari Ailus