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Date: Wed, 8 Feb 2017 13:36:24 +0000
From: Daniel Thompson <daniel.thompson@...aro.org>
To: Olimpiu Dejeu <olimpiu@...ticsand.com>, robh@...nel.org
Cc: lee.jones@...aro.org, linux-kernel@...r.kernel.org,
linux-fbdev@...r.kernel.org, devicetree@...r.kernel.org,
jingoohan1@...il.com, bdodge@...ticsand.com, joe@...ches.com,
medasaro@...ticsand.com
Subject: Re: [PATCH v5 1/2] backlight arcxcnn add support for ArcticSand
devices
On 30/01/17 23:01, Olimpiu Dejeu wrote:
> diff --git a/drivers/video/backlight/arcxcnn_bl.c b/drivers/video/backlight/arcxcnn_bl.c
> new file mode 100644
> index 0000000..284df08
> --- /dev/null
> +++ b/drivers/video/backlight/arcxcnn_bl.c
> @@ -0,0 +1,451 @@
> +/*
> + * Backlight driver for ArcticSand ARC_X_C_0N_0N Devices
> + *
> + * Copyright 2016 ArcticSand, Inc.
> + * Author : Brian Dodge <bdodge@...ticsand.com>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2
> + * as published by the Free Software Foundation.
> + *
> + * 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/>.
> + */
> +
> +#include <linux/backlight.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/slab.h>
> +
> +#include "linux/i2c/arcxcnn.h"
> +
> +#define ARCXCNN_CMD 0x00 /* Command Register */
> +#define ARCXCNN_CMD_STDBY 0x80 /* I2C Standby */
> +#define ARCXCNN_CMD_RESET 0x40 /* Reset */
> +#define ARCXCNN_CMD_BOOST 0x10 /* Boost */
> +#define ARCXCNN_CMD_OVP_MASK 0x0C /* --- Over Voltage Threshold */
> +#define ARCXCNN_CMD_OVP_XXV 0x0C /* <rsvrd> Over Voltage Threshold */
> +#define ARCXCNN_CMD_OVP_20V 0x08 /* 20v Over Voltage Threshold */
> +#define ARCXCNN_CMD_OVP_24V 0x04 /* 24v Over Voltage Threshold */
> +#define ARCXCNN_CMD_OVP_31V 0x00 /* 31.4v Over Voltage Threshold */
> +#define ARCXCNN_CMD_EXT_COMP 0x01 /* part (0) or full (1) ext. comp */
> +
> +#define ARCXCNN_CONFIG 0x01 /* Configuration */
> +#define ARCXCNN_STATUS1 0x02 /* Status 1 */
> +#define ARCXCNN_STATUS2 0x03 /* Status 2 */
> +#define ARCXCNN_FADECTRL 0x04 /* Fading Control */
> +#define ARCXCNN_ILED_CONFIG 0x05 /* ILED Configuration */
> +#define ARCXCNN_ILED_DIM_PWM 0x00 /* config dim mode pwm */
> +#define ARCXCNN_ILED_DIM_INT 0x04 /* config dim mode internal */
> +#define ARCXCNN_LEDEN 0x06 /* LED Enable Register */
> +#define ARCXCNN_LEDEN_ISETEXT 0x80 /* Full-scale current set extern */
> +#define ARCXCNN_LEDEN_MASK 0x3F /* LED string enables mask */
> +#define ARCXCNN_LEDEN_BITS 0x06 /* Bits of LED string enables */
> +#define ARCXCNN_LEDEN_LED1 0x01
> +#define ARCXCNN_LEDEN_LED2 0x02
> +#define ARCXCNN_LEDEN_LED3 0x04
> +#define ARCXCNN_LEDEN_LED4 0x08
> +#define ARCXCNN_LEDEN_LED5 0x10
> +#define ARCXCNN_LEDEN_LED6 0x20
> +
> +#define ARCXCNN_WLED_ISET_LSB 0x07 /* LED ISET LSB (in upper nibble) */
> +#define ARCXCNN_WLED_ISET_LSB_SHIFT 0x04 /* ISET LSB Left Shift */
> +#define ARCXCNN_WLED_ISET_MSB 0x08 /* LED ISET MSB (8 bits) */
> +
> +#define ARCXCNN_DIMFREQ 0x09
> +#define ARCXCNN_COMP_CONFIG 0x0A
> +#define ARCXCNN_FILT_CONFIG 0x0B
> +#define ARCXCNN_IMAXTUNE 0x0C
> +#define ARCXCNN_ID_MSB 0x1E
> +#define ARCXCNN_ID_LSB 0x1F
> +
> +#define MAX_BRIGHTNESS 4095
> +
> +static int no_reset_on_remove;
> +module_param_named(noreset, no_reset_on_remove, int, 0644);
> +MODULE_PARM_DESC(noreset, "No reset on module removal");
> +
> +static int ibright = 60;
> +module_param_named(ibright, ibright, int, 0644);
Use module_param() when names match.
> +MODULE_PARM_DESC(ibright, "Initial brightness (when no plat data)");
When will there be no platform data. Hotpluggable I2C backlight
controllers aren't very common.
Also, if this *is* needed, shouldn't the permissions should be 0444?
> +
> +static int ileden = ARCXCNN_LEDEN_MASK;
> +module_param_named(ileden, ileden, int, 0644);
> +MODULE_PARM_DESC(ileden, "Initial LED String Enables (when no plat data)");
Both, as above.
> +
> +struct arcxcnn {
> + char chipname[64];
This is more than double the size required. Actually if the chipid is
useful to userspace it should be stored numerically.
> + struct i2c_client *client;
> + struct backlight_device *bl;
> + struct device *dev;
> + struct arcxcnn_platform_data *pdata;
> +};
> +
> +static int arcxcnn_update_bit(struct arcxcnn *lp, u8 reg, u8 mask, u8 data)
s/_bit/_field/
> +{
> + int ret;
> + u8 tmp;
> +
> + ret = i2c_smbus_read_byte_data(lp->client, reg);
> + if (ret < 0) {
> + dev_err(lp->dev, "failed to read 0x%.2x\n", reg);
> + return ret;
> + }
> +
> + tmp = (u8)ret;
> + tmp &= ~mask;
> + tmp |= data & mask;
> +
> + return i2c_smbus_write_byte_data(lp->client, reg, tmp);
> +}
> +
> +static int arcxcnn_set_brightness(struct arcxcnn *lp, u32 brightness)
> +{
> + int ret;
> + u8 val;
> +
> + /* lower nibble of brightness goes in upper nibble of LSB register */
> + val = (brightness & 0xF) << ARCXCNN_WLED_ISET_LSB_SHIFT;
> + ret = i2c_smbus_write_byte_data(lp->client, ARCXCNN_WLED_ISET_LSB, val);
> + if (ret < 0)
> + return ret;
> +
> + /* remaining 8 bits of brightness go in MSB register */
> + val = (brightness >> 4);
> + ret = i2c_smbus_write_byte_data(lp->client, ARCXCNN_WLED_ISET_MSB, val);
> +
> + return ret;
This can be a direct return from _write_byte_data.
> +}
> +
> +static int arcxcnn_bl_update_status(struct backlight_device *bl)
> +{
> + struct arcxcnn *lp = bl_get_data(bl);
> + u32 brightness = bl->props.brightness;
> +
> + if (bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
> + brightness = 0;
> +
> + arcxcnn_set_brightness(lp, brightness);
Return code is ignored here...
> +
> + /* set power-on/off/save modes */
> + arcxcnn_update_bit(lp, ARCXCNN_CMD, ARCXCNN_CMD_STDBY,
> + (bl->props.power == 0) ? 0 : ARCXCNN_CMD_STDBY);
... and here.
> + return 0;
> +}
> +
> +static const struct backlight_ops arcxcnn_bl_ops = {
> + .options = BL_CORE_SUSPENDRESUME,
> + .update_status = arcxcnn_bl_update_status,
> +};
> +
> +static int arcxcnn_backlight_register(struct arcxcnn *lp)
> +{
> + struct backlight_properties *props;
> + const char *name = lp->pdata->name ? : "arctic_bl";
> +
> + props = devm_kzalloc(lp->dev, sizeof(*props), GFP_KERNEL);
> + if (!props)
> + return -ENOMEM;
> +
> + props->type = BACKLIGHT_PLATFORM;
> + props->max_brightness = MAX_BRIGHTNESS;
> +
> + if (lp->pdata->initial_brightness > props->max_brightness)
> + lp->pdata->initial_brightness = props->max_brightness;
> +
> + props->brightness = lp->pdata->initial_brightness;
> +
> + lp->bl = devm_backlight_device_register(lp->dev, name, lp->dev, lp,
> + &arcxcnn_bl_ops, props);
> + if (IS_ERR(lp->bl))
> + return PTR_ERR(lp->bl);
> +
> + return 0;
> +}
> +
> +static ssize_t arcxcnn_chip_id_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct arcxcnn *lp = dev_get_drvdata(dev);
> +
> + return scnprintf(buf, PAGE_SIZE, "%s\n", lp->chipname);
> +}
> +
> +static ssize_t arcxcnn_leden_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct arcxcnn *lp = dev_get_drvdata(dev);
> +
> + return scnprintf(buf, PAGE_SIZE, "%02X\n", lp->pdata->leden);
> +}
> +
> +static ssize_t arcxcnn_leden_store(struct device *dev,
> + struct device_attribute *attr, const char *buf, size_t len)
Under what circumstances can the led-sources change at runtime and
motivate this kind of interface?
> +{
> + struct arcxcnn *lp = dev_get_drvdata(dev);
> + unsigned long leden;
> +
> + if (kstrtoul(buf, 0, &leden))
> + return 0;
> +
> + if (leden != lp->pdata->leden) {
> + /* don't allow 0 for leden, use power to turn all off */
> + if (leden == 0)
> + return -EINVAL;
> + lp->pdata->leden = leden & ARCXCNN_LEDEN_MASK;
> + arcxcnn_update_bit(lp, ARCXCNN_LEDEN,
> + ARCXCNN_LEDEN_MASK, lp->pdata->leden);
Should be a return (to pass the error code back).
> + }
> +
> + return len;
> +}
> +
> +static DEVICE_ATTR(chip_id, 0444, arcxcnn_chip_id_show, NULL);
> +static DEVICE_ATTR(leden, 0664, arcxcnn_leden_show, arcxcnn_leden_store);
> +
> +static struct attribute *arcxcnn_attributes[] = {
> + &dev_attr_chip_id.attr,
> + &dev_attr_leden.attr,
> + NULL,
> +};
> +
> +static const struct attribute_group arcxcnn_attr_group = {
> + .attrs = arcxcnn_attributes,
> +};
> +
> +static void arcxcnn_parse_dt(struct arcxcnn *lp)
> +{
> + struct device *dev = lp->dev;
> + struct device_node *node = dev->of_node;
> + u32 prog_val, num_entry, entry, sources[ARCXCNN_LEDEN_BITS];
> + int ret;
> +
> + /* device tree entry isn't required, defaults are OK */
> + if (!node)
> + return;
> +
> + ret = of_property_read_string(node, "label", &lp->pdata->name);
> + if (ret < 0)
> + lp->pdata->name = NULL;
> +
> + ret = of_property_read_u32(node, "default-brightness", &prog_val);
> + if (ret == 0)
> + lp->pdata->initial_brightness = prog_val;
> +
> + ret = of_property_read_u32(node, "arc,led-config-0", &prog_val);
> + if (ret == 0)
> + lp->pdata->led_config_0 = (u8)prog_val;
> +
> + ret = of_property_read_u32(node, "arc,led-config-1", &prog_val);
> + if (ret == 0)
> + lp->pdata->led_config_1 = (u8)prog_val;
> +
> + ret = of_property_read_u32(node, "arc,dim-freq", &prog_val);
> + if (ret == 0)
> + lp->pdata->dim_freq = (u8)prog_val;
> +
> + ret = of_property_read_u32(node, "arc,comp-config", &prog_val);
> + if (ret == 0)
> + lp->pdata->comp_config = (u8)prog_val;
> +
> + ret = of_property_read_u32(node, "arc,filter-config", &prog_val);
> + if (ret == 0)
> + lp->pdata->filter_config = (u8)prog_val;
> +
> + ret = of_property_read_u32(node, "arc,trim-config", &prog_val);
> + if (ret == 0)
> + lp->pdata->trim_config = (u8)prog_val;
> +
> + ret = of_property_count_u32_elems(node, "led-sources");
> + if (ret < 0) {
> + lp->pdata->leden = ARCXCNN_LEDEN_MASK; /* all on is default */
> + } else {
> + num_entry = ret;
> + if (num_entry > ARCXCNN_LEDEN_BITS)
> + num_entry = ARCXCNN_LEDEN_BITS;
> +
> + ret = of_property_read_u32_array(node, "led-sources", sources,
> + num_entry);
> + if (ret < 0) {
> + dev_err(dev, "led-sources node is invalid.\n");
> + return;
> + }
> +
> + lp->pdata->leden = 0;
> +
> + /* for each enable in source, set bit in led enable */
> + for (entry = 0; entry < num_entry; entry++) {
> + u8 onbit = 1 << sources[entry];
> + lp->pdata->leden |= onbit;
> + }
> + }
> +}
> +
> +static int arcxcnn_probe(struct i2c_client *cl, const struct i2c_device_id *id)
> +{
> + struct arcxcnn *lp;
> + int ret;
> + u8 regval;
> + u16 chipid;
> +
> + if (!i2c_check_functionality(cl->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
> + return -EIO;
> +
> + lp = devm_kzalloc(&cl->dev, sizeof(*lp), GFP_KERNEL);
> + if (!lp)
> + return -ENOMEM;
> +
> + lp->client = cl;
> + lp->dev = &cl->dev;
> + lp->pdata = dev_get_platdata(&cl->dev);
> +
> + /* reset the device */
> + i2c_smbus_write_byte_data(lp->client,
> + ARCXCNN_CMD, ARCXCNN_CMD_RESET);
> +
> + /* read device ID */
> + regval = i2c_smbus_read_byte_data(lp->client, ARCXCNN_ID_MSB);
> + chipid = regval;
> + chipid <<= 8;
> +
> + regval = i2c_smbus_read_byte_data(lp->client, ARCXCNN_ID_LSB);
> + chipid |= regval;
> +
> + snprintf(lp->chipname, sizeof(lp->chipname),
> + "%s-%04X", id->name, chipid);
I'm curious what the chip id is and why the id is a userspace concern
rather than something the *driver* uses to confirm the probe is correct.
> +
> + if (!lp->pdata) {
> + lp->pdata = devm_kzalloc(lp->dev,
> + sizeof(*lp->pdata), GFP_KERNEL);
> + if (!lp->pdata)
> + return -ENOMEM;
> +
> + /* Setup defaults based on power-on defaults */
> + lp->pdata->name = NULL;
> + lp->pdata->initial_brightness = ibright;
> + lp->pdata->leden = ileden;
> +
> + lp->pdata->led_config_0 = i2c_smbus_read_byte_data(
> + lp->client, ARCXCNN_FADECTRL);
> +
> + lp->pdata->led_config_1 = i2c_smbus_read_byte_data(
> + lp->client, ARCXCNN_ILED_CONFIG);
> + /* insure dim mode is not default pwm */
> + lp->pdata->led_config_1 |= ARCXCNN_ILED_DIM_INT;
> +
> + lp->pdata->dim_freq = i2c_smbus_read_byte_data(
> + lp->client, ARCXCNN_DIMFREQ);
> +
> + lp->pdata->comp_config = i2c_smbus_read_byte_data(
> + lp->client, ARCXCNN_COMP_CONFIG);
> +
> + lp->pdata->filter_config = i2c_smbus_read_byte_data(
> + lp->client, ARCXCNN_FILT_CONFIG);
> +
> + lp->pdata->trim_config = i2c_smbus_read_byte_data(
> + lp->client, ARCXCNN_IMAXTUNE);
> +
> + if (IS_ENABLED(CONFIG_OF))
> + arcxcnn_parse_dt(lp);
> + }
> +
> + i2c_set_clientdata(cl, lp);
> +
> + /* constrain settings to what is possible */
> + if (lp->pdata->initial_brightness > MAX_BRIGHTNESS)
> + lp->pdata->initial_brightness = MAX_BRIGHTNESS;
> +
> + /* set initial brightness */
> + arcxcnn_set_brightness(lp, lp->pdata->initial_brightness);
> +
> + /* set other register values directly */
> + i2c_smbus_write_byte_data(lp->client, ARCXCNN_FADECTRL,
> + lp->pdata->led_config_0);
> + i2c_smbus_write_byte_data(lp->client, ARCXCNN_ILED_CONFIG,
> + lp->pdata->led_config_1);
> + i2c_smbus_write_byte_data(lp->client, ARCXCNN_DIMFREQ,
> + lp->pdata->dim_freq);
> + i2c_smbus_write_byte_data(lp->client, ARCXCNN_COMP_CONFIG,
> + lp->pdata->comp_config);
> + i2c_smbus_write_byte_data(lp->client, ARCXCNN_FILT_CONFIG,
> + lp->pdata->filter_config);
> + i2c_smbus_write_byte_data(lp->client, ARCXCNN_IMAXTUNE,
> + lp->pdata->trim_config);
> +
> + /* set initial LED Enables */
> + arcxcnn_update_bit(lp, ARCXCNN_LEDEN,
> + ARCXCNN_LEDEN_MASK, lp->pdata->leden);
Pretty much *all* of the above functions return error codes.
> + ret = arcxcnn_backlight_register(lp);
> + if (ret) {
> + dev_err(lp->dev,
> + "failed to register backlight. err: %d\n", ret);
> + return ret;
> + }
> +
> + ret = sysfs_create_group(&lp->dev->kobj, &arcxcnn_attr_group);
> + if (ret) {
> + dev_err(lp->dev, "failed to register sysfs. err: %d\n", ret);
> + return ret;
> + }
> +
> + backlight_update_status(lp->bl);
> +
> + return 0;
> +}
> +
> +static int arcxcnn_remove(struct i2c_client *cl)
> +{
> + struct arcxcnn *lp = i2c_get_clientdata(cl);
> +
> + if (!no_reset_on_remove) {
> + /* disable all strings */
> + i2c_smbus_write_byte_data(lp->client,
> + ARCXCNN_LEDEN, 0x00);
> + /* reset the device */
> + i2c_smbus_write_byte_data(lp->client,
> + ARCXCNN_CMD, ARCXCNN_CMD_RESET);
> + }
Why would userspace want to suppress this reset?
> + lp->bl->props.brightness = 0;
> +
> + backlight_update_status(lp->bl);
> +
> + sysfs_remove_group(&lp->dev->kobj, &arcxcnn_attr_group);
> +
> + return 0;
> +}
> +
> +static const struct of_device_id arcxcnn_dt_ids[] = {
> + { .compatible = "arc,arc2c0608" },
> + { }
> +};
> +MODULE_DEVICE_TABLE(of, arcxcnn_dt_ids);
> +
> +static const struct i2c_device_id arcxcnn_ids[] = {
> + {"arc2c0608", ARC2C0608},
> + { }
> +};
> +MODULE_DEVICE_TABLE(i2c, arcxcnn_ids);
> +
> +static struct i2c_driver arcxcnn_driver = {
> + .driver = {
> + .name = "arcxcnn_bl",
> + .of_match_table = of_match_ptr(arcxcnn_dt_ids),
> + },
> + .probe = arcxcnn_probe,
> + .remove = arcxcnn_remove,
> + .id_table = arcxcnn_ids,
> +};
> +module_i2c_driver(arcxcnn_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Brian Dodge <bdodge@...ticsand.com>");
> +MODULE_DESCRIPTION("ARCXCNN Backlight driver");
> diff --git a/include/linux/i2c/arcxcnn.h b/include/linux/i2c/arcxcnn.h
> new file mode 100644
> index 0000000..e378d63
> --- /dev/null
> +++ b/include/linux/i2c/arcxcnn.h
There's a general trend to move unused header files out of this
directory and fold things back into the C code.
Are you expecting to add anything to the kernel (other than the driver)
that actually includes this header, if not we probably don't need it.
Daniel.
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