Method find_partition_of_esp_optional

crates/blockdev/src/blockdev.rs:252–285

Find the EFI System Partition (ESP) among children. For GPT disks, this matches by the ESP partition type GUID. For MBR (dos) disks, this matches by the MBR partition type IDs (0x06 or 0xEF). If no ESP is found among direct children, this recurses into children that have their own partition table (e.g. firmware RAID arrays where the hierarchy is disk → md array → partitions). Returns `Ok(None)`

(&self)

    /// is present. Returns `Err` only for genuinely unexpected conditions
    /// (e.g. an unsupported partition table type).
    pub fn find_partition_of_esp_optional(&self) -> Result<Option<&Device>> {
        let Some(children) = self.children.as_ref() else {
            return Ok(None);
        };
        let direct = match self.pttype.as_deref() {
            Some("dos") => children.iter().find(|child| {
                child
                    .parttype
                    .as_ref()
                    .and_then(|pt| {
                        let pt = pt.strip_prefix("0x").unwrap_or(pt);
                        u8::from_str_radix(pt, 16).ok()
                    })
                    .is_some_and(|pt| ESP_ID_MBR.contains(&pt))
            }),
            // When pttype is None (e.g. older lsblk or partition devices), default
            // to GPT UUID matching which will simply not match MBR hex types.
            Some("gpt") | None => self.find_partition_of_type(ESP),
            Some(other) => return Err(anyhow!("Unsupported partition table type: {other}")),
        };
        if direct.is_some() {
            return Ok(direct);
        }
        // Recurse into children that carry their own partition table, such as
        // firmware RAID arrays (disk → md array → partitions).
        for child in children {
            if child.pttype.is_some() {
                if let Some(esp) = child.find_partition_of_esp_optional()? {
                    return Ok(Some(esp));
                }
            }
        }
        Ok(None)
    }

    /// Find the EFI System Partition (ESP) among children, or error if absent.
    ///