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d="scan'208";a="216051388" Received: from soc-5cg43972f8.clients.intel.com (HELO [172.28.182.57]) ([172.28.182.57]) by ORVIESA003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Feb 2026 02:19:04 -0800 Message-ID: <1c068311-2769-4f90-9c7c-9733a45d9029@linux.intel.com> Date: Tue, 10 Feb 2026 11:19:01 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 i-g-t 2/7] lib/igt_pci: Add generic PCI driver override and bind/unbind helpers To: "Laguna, Lukasz" , igt-dev@lists.freedesktop.org Cc: Adam Miszczak , Jakub Kolakowski , Kamil Konieczny References: <20260204163217.121305-1-marcin.bernatowicz@linux.intel.com> <20260204163217.121305-3-marcin.bernatowicz@linux.intel.com> <2ebfcc0d-49ca-4fde-a48f-27a014b5f729@intel.com> Content-Language: en-US From: "Bernatowicz, Marcin" In-Reply-To: <2ebfcc0d-49ca-4fde-a48f-27a014b5f729@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: igt-dev@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development mailing list for IGT GPU Tools List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: igt-dev-bounces@lists.freedesktop.org Sender: "igt-dev" On 2/9/2026 11:16 AM, Laguna, Lukasz wrote: > > On 2/4/2026 17:32, Marcin Bernatowicz wrote: >> Add generic helpers for controlling PCI driver binding via sysfs. >> >> The new APIs provide driver- and device-centric primitives for: >>    - setting and clearing driver_override >>    - triggering PCI driver reprobe >>    - binding and unbinding devices to a specific PCI driver >>    - query the currently bound PCI driver >> >> Signed-off-by: Marcin Bernatowicz >> Cc: Adam Miszczak >> Cc: Jakub Kolakowski >> Cc: Kamil Konieczny >> Cc: Lukasz Laguna >> >> --- >> v2: >> - Add igt_pci_get_bound_driver_name() to query the currently bound PCI >>    driver via the /sys/bus/pci/devices//driver symlink. >> - Extend igt_pci_bind_driver_override() and >> igt_pci_unbind_driver_override() >>    with a timeout_ms parameter so callers can wait for bind/unbind to >>    actually complete, instead of relying on drivers_probe write success. >> >> --- >>   lib/igt_pci.c | 351 ++++++++++++++++++++++++++++++++++++++++++++++++++ >>   lib/igt_pci.h |  13 +- >>   2 files changed, 363 insertions(+), 1 deletion(-) >> >> diff --git a/lib/igt_pci.c b/lib/igt_pci.c >> index 61aaf939d..80aaf07c5 100644 >> --- a/lib/igt_pci.c >> +++ b/lib/igt_pci.c >> @@ -3,9 +3,18 @@ >>    * Copyright © 2022 Intel Corporation >>    */ >>   +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >>   #include >> +#include "igt_aux.h" >>   #include "igt_core.h" >>   #include "igt_pci.h" >> +#include "igt_sysfs.h" >>     static int find_pci_cap_offset_at(struct pci_device *dev, enum >> pci_cap_id cap_id, >>                     int start_offset) >> @@ -51,3 +60,345 @@ int find_pci_cap_offset(struct pci_device *dev, >> enum pci_cap_id cap_id) >>   { >>       return find_pci_cap_offset_at(dev, cap_id, PCI_CAPS_START); >>   } >> + >> +static int open_pci_driver_dir(const char *driver) >> +{ >> +    char path[PATH_MAX]; >> + >> +    snprintf(path, sizeof(path), "/sys/bus/pci/drivers/%s", driver); >> +    return open(path, O_RDONLY | O_CLOEXEC); >> +} >> + >> +/** >> + * igt_pci_device_unbind: >> + * @pci_slot: BDF like "0000:01:00.0" >> + * >> + * Unbind @pci_slot from its currently bound driver, if any. >> + * Returns 0 on success, or a negative errno-like value. >> + */ >> +int igt_pci_device_unbind(const char *pci_slot) >> +{ >> +    char path[PATH_MAX]; >> +    int dirfd; >> +    int ret; >> + >> +    snprintf(path, sizeof(path), "/sys/bus/pci/devices/%s/driver", >> pci_slot); >> +    dirfd = open(path, O_RDONLY | O_CLOEXEC); >> +    if (dirfd < 0) >> +        return 0; /* already unbound */ >> + >> +    ret = igt_sysfs_set(dirfd, "unbind", pci_slot) ? 0 : -errno; >> +    close(dirfd); >> + >> +    return ret; >> +} >> + >> +/** >> + * igt_pci_driver_bind: >> + * @driver: PCI driver name under /sys/bus/pci/drivers/ >> + * @pci_slot: device to bind >> + * >> + * Bind @pci_slot to @driver. Driver must be present/loaded. >> + * Returns 0 on success, or a negative errno-like value. >> + */ >> +int igt_pci_driver_bind(const char *driver, const char *pci_slot) >> +{ >> +    int dirfd, ret; >> + >> +    dirfd = open_pci_driver_dir(driver); >> +    if (dirfd < 0) >> +        return -errno; >> + >> +    ret = igt_sysfs_set(dirfd, "bind", pci_slot) ? 0 : -errno; >> +    close(dirfd); >> + >> +    return ret; >> +} >> + >> +/** >> + * igt_pci_driver_unbind: >> + * @driver: PCI driver name >> + * @pci_slot: device to unbind >> + * >> + * Unbind @pci_slot from @driver. >> + * Returns 0 on success, or a negative errno-like value. >> + */ >> +int igt_pci_driver_unbind(const char *driver, const char *pci_slot) >> +{ >> +    int dirfd, ret; >> + >> +    dirfd = open_pci_driver_dir(driver); >> +    if (dirfd < 0) >> +        return -errno; >> + >> +    ret = igt_sysfs_set(dirfd, "unbind", pci_slot) ? 0 : -errno; >> +    close(dirfd); >> + >> +    return ret; >> +} >> + >> +/** >> + * igt_pci_driver_unbind_all: >> + * @driver: PCI driver name >> + * >> + * Unbind all devices currently bound to @driver. >> + * Returns 0 on success, or a negative errno-like value. >> + */ >> +int igt_pci_driver_unbind_all(const char *driver) >> +{ >> +    char path[PATH_MAX]; >> +    DIR *dir; >> +    struct dirent *de; >> +    int driver_fd; >> + >> +    snprintf(path, sizeof(path), "/sys/bus/pci/drivers/%s", driver); >> +    dir = opendir(path); >> +    if (!dir) >> +        return -errno; >> + >> +    driver_fd = dirfd(dir); >> + >> +    while ((de = readdir(dir))) { >> +        bool ok; >> + >> +        /* BDF symlinks are like "0000:01:00.0" and start with digit */ >> +        if (de->d_type != DT_LNK || !isdigit(de->d_name[0])) >> +            continue; >> + >> +        ok = igt_sysfs_set(driver_fd, "unbind", de->d_name); >> +        if (!ok) { >> +            int err = -errno; >> + >> +            closedir(dir); >> +            return err; >> +        } >> +    } >> + >> +    closedir(dir); >> +    return 0; >> +} >> + >> +/** >> + * igt_pci_set_driver_override: >> + * @pci_slot: PCI device BDF (e.g. "0000:01:00.0") >> + * @driver: PCI driver name to force-bind (e.g. "xe-vfio-pci"), or >> + *          NULL / empty string to clear an existing override >> + * >> + * Set or clear the PCI driver_override for @pci_slot via sysfs. >> + * >> + * This does not trigger driver reprobe by itself. Call >> + * igt_pci_probe_drivers() afterwards to apply the override. >> + * >> + * Returns: 0 on success, negative errno on failure. >> + */ >> +int igt_pci_set_driver_override(const char *pci_slot, const char >> *driver) >> +{ >> +    char devpath[PATH_MAX]; >> +    int dev; >> +    bool ok; >> + >> +    snprintf(devpath, sizeof(devpath), "/sys/bus/pci/devices/%s", >> pci_slot); >> +    dev = open(devpath, O_DIRECTORY | O_RDONLY); >> +    if (dev < 0) >> +        return -errno; >> + >> +    ok = igt_sysfs_set(dev, "driver_override", driver ? driver : ""); >> +    close(dev); >> + >> +    return ok ? 0 : -errno; >> +} >> + >> +/** >> + * igt_pci_probe_drivers: >> + * @pci_slot: PCI device BDF (e.g. "0000:01:00.0") >> + * >> + * Trigger PCI driver reprobe for @pci_slot by writing to >> + * /sys/bus/pci/drivers_probe. >> + * >> + * This causes the kernel to attempt binding the device, honoring any >> + * driver_override previously set. >> + * >> + * Note: a successful write only means the reprobe request was >> accepted. >> + * It does not guarantee that a driver actually bound to the device. >> + * >> + * Returns: 0 on success, negative errno on failure. >> + */ >> +int igt_pci_probe_drivers(const char *pci_slot) >> +{ >> +    int pci; >> +    bool ok; >> + >> +    pci = open("/sys/bus/pci", O_DIRECTORY | O_RDONLY); >> +    if (pci < 0) >> +        return -errno; >> + >> +    ok = igt_sysfs_set(pci, "drivers_probe", pci_slot); >> +    close(pci); >> + >> +    return ok ? 0 : -errno; >> +} >> + >> +/** >> + * igt_pci_get_bound_driver_name: >> + * @pci_slot: PCI device BDF (e.g. "0000:01:00.0") >> + * @driver: destination buffer for the bound driver name >> + * @driver_len: size of @driver in bytes >> + * >> + * Read the currently bound PCI driver name for @pci_slot by >> inspecting the >> + * /sys/bus/pci/devices//driver symlink. >> + * >> + * Return values: >> + *  1: device is bound and @driver contains the driver name >> + *  0: device is unbound (no driver symlink) >> + * <0: negative errno-like value on error >> + */ >> +int igt_pci_get_bound_driver_name(const char *pci_slot, char >> *driver, size_t driver_len) >> +{ >> +    char path[PATH_MAX]; >> +    char link[PATH_MAX]; >> +    const char *base; >> +    ssize_t len; >> + >> +    if (driver && driver_len) >> +        driver[0] = '\0'; >> + >> +    snprintf(path, sizeof(path), "/sys/bus/pci/devices/%s/driver", >> pci_slot); >> +    len = readlink(path, link, sizeof(link) - 1); >> +    if (len < 0) { >> +        if (errno == ENOENT) >> +            return 0; /* unbound */ >> + >> +        return -errno; >> +    } >> + >> +    link[len] = '\0'; >> +    base = strrchr(link, '/'); >> +    base = base ? base + 1 : link; >> + >> +    if (driver && driver_len) > > You can check the input params at the beginning of the function and > return error if they are invalid. driver/driver_len are optional, callers may pass NULL and/or 0 when they only need the return value (bound/unbound) and don’t care about the driver name... > >> +        snprintf(driver, driver_len, "%s", base); >> + >> +    return 1; >> +} >> + >> +/** >> + * igt_pci_bind_driver_override: >> + * @pci_slot: PCI device BDF (e.g. "0000:01:00.0") >> + * @driver: PCI driver name to bind (must not be NULL or empty) >> + * @timeout_ms: how long to wait for the device to become bound. >> + *              If 0, don't wait (best-effort immediate check only). >> + * >> + * Bind @pci_slot to @driver using the driver_override mechanism. >> + * >> + * This helper sets driver_override and immediately triggers driver >> + * reprobe so that the device is bound to the requested driver. >> + * >> + * Returns: 0 on success, negative errno-like value on failure. >> + * A reprobe request can be accepted by sysfs while the driver probe >> + * fails later; this helper verifies the device ended up bound. >> + * >> + * On bind failure, returns a negative error and the failure reason may >> + * also be logged to dmesg by the kernel driver. >> + */ >> +int igt_pci_bind_driver_override(const char *pci_slot, const char >> *driver, >> +                 unsigned int timeout_ms) >> +{ >> +    int ret; >> +    char bound[64]; >> +    int bound_ret; >> +    bool bound_ok; >> + >> +    if (!driver || !driver[0]) >> +        return -EINVAL; >> + >> +    ret = igt_pci_set_driver_override(pci_slot, driver); >> +    if (ret) >> +        return ret; >> + >> +    ret = igt_pci_probe_drivers(pci_slot); >> +    if (ret) >> +        return ret; >> + >> +    /* >> +     * Writing to drivers_probe only tells us the kernel accepted >> the request. >> +     * The actual driver probe may still fail (and only be reported >> via dmesg). >> +     * Verify that the device ended up bound to the requested driver. >> +     */ >> +    bound_ret = igt_pci_get_bound_driver_name(pci_slot, bound, >> sizeof(bound)); >> +    if (bound_ret < 0) >> +        return bound_ret; >> + >> +    if (timeout_ms == 0) { >> +        /* >> +         * No waiting requested. If the device is already bound, >> validate >> +         * it is bound to the expected driver; otherwise treat as >> +         * best-effort request-only success. >> +         */ >> +        if (bound_ret > 0 && strcmp(bound, driver)) >> +            return -EBUSY; >> + >> +        return 0; >> +    } >> + >> +    bound_ok = igt_wait((bound_ret = >> +                 igt_pci_get_bound_driver_name(pci_slot, bound, >> sizeof(bound))) != 0, >> +                timeout_ms, 1); >> +    if (!bound_ok) >> +        return -EIO; >> + >> +    if (bound_ret < 0) >> +        return bound_ret; >> + >> +    if (strcmp(bound, driver)) >> +        return -EBUSY; >> + >> +    return 0; >> +} >> + >> +/** >> + * igt_pci_unbind_driver_override: >> + * @pci_slot: PCI device BDF (e.g. "0000:01:00.0") >> + * @timeout_ms: how long to wait for the device to become unbound. >> + *              If 0, don't wait (best-effort immediate check only). >> + * >> + * Unbind @pci_slot from its currently bound driver (if any) and clear >> + * any driver_override setting. >> + * >> + * This is the inverse operation of igt_pci_bind_driver_override(). >> + * >> + * Returns: 0 on success, negative errno on failure. >> + */ >> +int igt_pci_unbind_driver_override(const char *pci_slot, unsigned >> int timeout_ms) >> +{ >> +    int ret; >> +    int bound_ret; >> +    char bound[64]; >> +    bool unbound_ok; >> + >> +    ret = igt_pci_device_unbind(pci_slot); >> +    if (ret) >> +        return ret; >> + >> +    ret = igt_pci_set_driver_override(pci_slot, ""); >> +    if (ret) >> +        return ret; >> + >> +    bound_ret = igt_pci_get_bound_driver_name(pci_slot, bound, >> sizeof(bound)); >> +    if (bound_ret < 0) >> +        return bound_ret; >> + >> +    if (timeout_ms == 0) >> +        return 0; >> + >> +    /* Verify the device actually ends up unbound (driver symlink >> removed). */ >> +    unbound_ok = igt_wait((bound_ret = >> +                   igt_pci_get_bound_driver_name(pci_slot, bound, >> sizeof(bound))) == 0, >> +                  timeout_ms, 1); >> +    if (!unbound_ok) >> +        return -EBUSY; >> + >> +    if (bound_ret < 0) >> +        return bound_ret; >> + >> +    return 0; >> +} >> diff --git a/lib/igt_pci.h b/lib/igt_pci.h >> index 92b9cc392..a66eeebf2 100644 >> --- a/lib/igt_pci.h >> +++ b/lib/igt_pci.h >> @@ -6,8 +6,9 @@ >>   #ifndef __IGT_PCI_H__ >>   #define __IGT_PCI_H__ >>   -#include >>   #include >> +#include >> +#include >>     /* forward declaration */ >>   struct pci_device; >> @@ -24,5 +25,15 @@ enum pci_cap_id { >>   #define  PCI_SLOT_PWR_CTRL_PRESENT (1 << 1) >>     int find_pci_cap_offset(struct pci_device *dev, enum pci_cap_id >> cap_id); >> +int igt_pci_device_unbind(const char *pci_slot); >> +int igt_pci_driver_bind(const char *driver, const char *pci_slot); >> +int igt_pci_driver_unbind(const char *driver, const char *pci_slot); >> +int igt_pci_driver_unbind_all(const char *driver); >> +int igt_pci_set_driver_override(const char *pci_slot, const char >> *driver); >> +int igt_pci_probe_drivers(const char *pci_slot); >> +int igt_pci_get_bound_driver_name(const char *pci_slot, char >> *driver, size_t driver_len); >> +int igt_pci_bind_driver_override(const char *pci_slot, const char >> *driver, >> +                 unsigned int timeout_ms); >> +int igt_pci_unbind_driver_override(const char *pci_slot, unsigned >> int timeout_ms); >>     #endif